Quick command reference

Quick command reference

[Paul Mackerras]

As an aid to my understanding of the core git commands, I created this
summary of the commands and their options and parameters.  I hope it
will be useful to others.  Corrections welcome of course.

Paul.
---

git-cat-file -t sha1-id
	Prints type of object with given sha1-id to stdout.

git-cat-file type sha1-id
	Copies contents of object with given sha1-id to stdout.
	Complains if type of sha1-id isn't of the type specified.

git-check-files pathname...
	Checks that each pathname given is up-to-date in the w.d.
	(i.e. matches the dircache) or is not present.

git-checkout-cache [-a] [-f] [-q] [-n] [--prefix=path] [--] [files...]
	Copies files from the git object repository to the
	working directory or another directory.  Does not rewrite
	files that already exist and match the dircache.
	-a: check out all files listed in dircache.
	-f: overwrite existing files; without this, checkout-cache
		will not overwrite an existing file even if it
		differs from what is in the dircache.
	-q: quiet; don't print an error message when a file is
		unmerged or not in the dircache, or when a file exists
		but differs from the dircache and -f was not given.
	-n: not new files; don't checkout any file that doesn't
		already exist in the dircache.
	--prefix=path: prepend path to the pathname of each file
		being checked out.  If you want to use this to
		check out files with their normal names but in
		another directory, make sure the path ends in /.
	The order of the flags matters; checkout-cache -a -f
	is different from checkout-cache -f -a.  Flags may be
	interspersed between file names.

git-commit-tree tree-id [-p parent-commit-id]* < changelog
	Generates a commit object referring to the given tree with
	the parent commit-ids given.  (If no parents are given, this
	is an initial commit.)  Prints the sha1 id of the generated
	commit to stdout.

git-diff-cache [-r] [-p] [-z] [--cached] tree-id
	Show differences between the tree identified by tree-id
	and the dircache and/or the working directory.
	-r: ignored (old recursive flag)
	-p: generate patches (full diff listings)
	-z: terminate lines with \0 instead of \n
	--cached: diff against last cached state rather than
	    file in w.d. for new or changed files.  New and changed
	    files are always identified by comparing dircache and
	    tree entries, but without this flag, the files that are
	    identified as new or changed are compared against the
	    working directory rather than the cached version.
	Unmerged (non-stage 0) entries in dircache are shown as:
		U <pathname>
	or if -p is given, as
		* Unmerged path pathname
	Files in tree but not in dircache (or w.d., without --cached):
		-mode<tab>blob<tab>sha1<tab>pathname
	or with -p, as a patch deleting the file.
	Files in dircache but not in tree are shown as:
		+mode<tab>blob<tab>sha1<tab>pathname
	or with -p, as a patch adding the file.
	Files that differ are shown as:
		*mode->mode<tab>blob<tab>sha1->sha1<tab>pathname
	or with -p, as a patch showing the differences

git-diff-files
	Compares working-directory with dircache and prints a listing
	of changed files.
	-p: generate patches (full diff listings)
	-q: Silent; don't show files missing from w.d.
	-r: ignored (old recursive flag)
	-s: ignored (old silent flag)
	-z: terminate lines with \0 instead of \n
	If no pathnames given, compare all files in dircache.
	Checks mode, uid, gid, size, mtime, ctime, dev/ino, size.
	Output is as for git-diff-cache ("-" indicates file in
	dircache but not in w.d.).

git-diff-tree [-p] [-r] [-z] tree1-id tree2-id
	Compares two trees identified by their ids.
	-p: generate patches (implies -r)
	-r: recursive
	-z: terminate lines with \0 instead of \n
	Output is as for git-diff-cache (except there are no unmerged
	entries, since they can only exist in the dircache).

git-diff-tree-helper [-R] [-z] pathname...
	Reads the output of git-diff-tree and generates diffs (patches)
	for the files listed on the command line.
	-R: generate reverse diff
	-z: expect input lines to be terminated with \0

git-export top-sha1 [base-sha1]
	top-sha1 and base-sha1 are commit-ids
	Outputs all the changesets to get to top-sha1, with patches.
	If base-sha1 is given, only outputs changesets from base-sha1
	to top-sha1.

git-fsck-cache [--tags] [--root] [--unreachable] head-sha1...
	Checks the consistency of the object repository.
	If given, the head-sha1 parameter(s) is/are the ids of
	one or more heads of the commit graph.

git-http-pull [-c] [-t] [-a] commit-id url
	-t: tree
	-c: commits
	-a: all
	Fetches the commit object with id commit-id.
	With -t or -a, fetches the tree and blobs for that commit-id.
	With -c or -a, fetches the parents, and recursively fetches
	each of their parents, etc.; with -a, fetches the tree and
	blobs for each of the ancestors as well.

git-init-db
	makes .git directory
	if SHA1_FILE_DIRECTORY not set, makes .git/objects/xx dirs

git-ls-files [-c|--cached] [-d|--deleted] [-o|--others] [-i|--ignored]
	[-s|--stage] [-u|--unmerged] [-x pattern|--exclude=pattern]
	[-X excl-file|--exclude-from=excl-file] [-z]
	Lists filenames from dircache.
	-c|--cached: list files in dircache (default)
	-d|--deleted: list files in dircache but not in w.d.
	-o|--others: list files in w.d. but not in dircache
	-i|--ignored: show files that would be excluded;
		requires at least one -x|-X|--exclude|--exclude-from
	-s|--stage: show full information including merge stage
		for each file
	-u|--unmerged: only show files with merge stage > 0 in dircache
	-x pattern|--exclude=pattern: exclude files matching pattern
	-X file|--exclude-from=file: read exclude patterns from
		file, one per line
	-z: terminate lines with \0 instead of \n
	Without -s, just prints pathnames, one per line.
	With -s, prints:
		mode sha1 stage pathname

git-ls-tree [-z] [-r] sha1
	prints contents of tree object in readable form
	4 columns: mode type sha1 name
	-z: terminate lines with \0 instead of \n
	-r: show subdirectories recursively

git-merge-base commit1-id commit2-id
	Finds the nearest common ancestor of commit1 and commit2,
	and prints its sha1 id

git-merge-cache <merge-program> [-a] [--] <filename>*
	-a: merge all files listed in dircache
	For each file to be merged, do nothing if it is at stage
	0 in the dircache.  Otherwise run:
		merge-program stage1-id stage2-id stage3-id \
		    pathname stage1-mode stage2-mode stage3-mode
	The stageX-id and stageX-mode are "" if that stage isn't
	present in the dircache for that file.

git-mktag < signature-file
	Verifies the input is a syntactically valid tag,
	creates an object containing the input, and prints
	its sha1 id.

git-read-tree (-m | stage0-sha1) [stage1-sha1] [stage2-sha1] [stage3-sha1]
	tree-object(s) -> dircache (uids, gids, inos, times, sizes == 0)
	-m: merge, i.e. start in stage 1; requires all objects in
	    dircache to be stage 0 initially; requires 1 or 3 trees.
	    With 1 tree, merges stat info from existing dircache
	    for unchanged files (same name and sha1 as tree).
	    With 3 trees, does a trivial 3-way merge.  Files merged
	    are made stage 0 and old stat info is used if possible.
	    Anything non-trivial is left as stage 1,2,3 entries.
	    Result goes into new index file.
	Without -m, existing dircache contents are discarded.
	Normally only one sha1 id would be given; more than one can be
	given but no merging is done.

git-rev-list commit-id
	prints the commit-ids of the ancestors of commit-id,
	ordered by date.

git-rev-tree [--edges] [^]commit-id [[^]commit-id]*
	--edges: show commits whose reachability differs from one or
	  more of its parents (reachability == which subset of the
	  commit-ids given on the command line it's reachable from).
	^ means don't show commits reachable from this commit-id
	  (ignored with --edges)
	each line of output is formatted as:
	  decimal-date commit-id:flags [parent-commit-id:flags]*
	flags is in decimal and is a reachability bitmap, i.e.
	0x1 is set if reachable from the first commit-id given,
	0x2 if reachable from the second, etc.

git-rpull [-t] [-c] [-a] commit-id url
	Flags are like http-pull.
	Pulls commits, trees and blobs from another machine over
	ssh; execs ssh to run rpush on the remote machine.
	url can be "-" meaning just talk over stdin/stdout
	instead of running ssh.

git-rpush [-t] [-c] [-a] commit-id url
	Flags are like http-pull.
	Pushes commits, tree and blobs from this machine to another
	machine over ssh; execs ssh to run rpull on the remote machine.
	url can be "-" meaning just talk over stdin/stdout
	instead of running ssh.

git-tar-tree sha1-id [basedir]
	Generates a tar-file on stdout for the tree identified by
	sha1-id, which can be a commit id or a tree id.
	If basedir is given, basedir/ is prepended to all pathnames.

git-unpack-file sha1-id
	Generates a temporary file name of the form .merge_file_XXXXXX
	and writes the contents of the blob object identified by sha1-id
	to it; outputs the generated name to stdout.

git-update-cache [--add] [--remove] [--] pathname...
	Update dircache entry for filename(s) from w.d.
	--add: add pathnames that are in w.d. but not dircache to
	    the dircache (without --add, print a message)
	--remove: remove pathnames which are in dircache but not
	    w.d. from the dircache (without --remove, print a message)

git-update-cache --refresh [--ignore-missing]
	Sets uid, gid, times, size on each entry in dircache from w.d.
	Complains if mode or data differs (assumes data matches
	if size and date match).
	Complains if any file not in w.d. unless --ignore-missing is given.

git-update-cache --cacheinfo mode sha1 path
	Adds an entry to the dircache for path with given mode and sha1.

git-write-tree
	Creates a tree object from the contents of the dircache
	(creating tree objects for subdirectories, recursively).
	Prints sha1 of top-level tree-object to stdout.
	Complains if any files are unmerged (merge stage > 0).

N.B.
w.d. = working directory (.)
dircache is in .git/index
object files are in $SHA1_FILE_DIRECTORY or .git/objects

Re: Quick command reference

[David Greaves]

[-- Attachment #1: Type: text/plain, Size: 542 bytes --]

Paul Mackerras wrote:

>As an aid to my understanding of the core git commands, I created this
>summary of the commands and their options and parameters.  I hope it
>will be useful to others.  Corrections welcome of course.
>
>Paul.
>  
>

Thanks Paul

Shame to see duplicated effort...

I've submitted this document to Linus and the list a few times and
included all the feedback but for some reason it's not gone into any of
the trees which means that people like you have to redo it from scratch...

Getting frustrated now...

David

-- 


[-- Attachment #2: README.reference --]
[-- Type: text/plain, Size: 35927 bytes --]

This file contains reference information for the core git commands.
It is actually based on the source from Petr Baudis' tree and may
therefore contain a few 'extras' that may or may not make it upstream.

The README contains much useful definition and clarification info -
read that first.  And of the commands, I suggest reading
'update-cache' and 'read-tree' first - I wish I had!

Thanks to original email authors and proof readers esp Junio C Hamano
<junkio@cox.net>

David Greaves <david@dgreaves.com>
24/4/05

Identifier terminology used:

<object>
	Indicates any object sha1 identifier

<blob>
	Indicates a blob object sha1 identifier

<tree>
	Indicates a tree object sha1 identifier

<commit>
	Indicates a commit object sha1 identifier

<tree/commit>
	Indicates a tree or commit object sha1 identifier (usually
	because the command can read the <tree> a <commit> contains).
	[Eventually may be replaced with <tree> if <tree> means
	<tree/commit> in all commands]

<type>
	Indicates that an object type is required.
	Currently one of: blob/tree/commit

<file>
	Indicates a filename - often includes leading path

<path>
	Indicates the path of a file (is this ever useful?)



################################################################
cat-file
	cat-file (-t | <type>) <object>

Provide contents or type of objects in the repository. The type is
required if -t is not being used to find the object type.

<object>
	The sha1 identifier of the object.

-t
	show the object type identified by <object>

<type>
	One of: blob/tree/commit

Output

If -t is specified, one of:
        blob/tree/commit

Otherwise the raw (though uncompressed) contents of the <object> will
be returned.


################################################################
check-files
	check-files <file>...

Check that a list of files are up-to-date between the filesystem and
the cache. Used to verify a patch target before doing a patch.

Files that do not exist on the filesystem are considered up-to-date
(whether or not they are in the cache).

Emits an error message on failure.
preparing to update existing file <file> not in cache
	  <file> exists but is not in the cache

preparing to update file <file> not uptodate in cache
	  <file> on disk is not up-to-date with the cache

exits with a status code indicating success if all files are
up-to-date.

see also: update-cache


################################################################
checkout-cache
	checkout-cache [-q] [-a] [-f] [-n] [--prefix=<string>]
		       [--] <file>...

Will copy all files listed from the cache to the working directory
(not overwriting existing files). Note that the file contents are
restored - NOT the file permissions.
??? l 58 checkout-cache.c says restore executable bit.

-q
	be quiet if files exist or are not in the cache

-f
	forces overwrite of existing files

-a
	checks out all files in the cache (will then continue to
	process listed files).
-n
	Don't checkout new files, only refresh files already checked
	out.

--prefix=<string>
	When creating files, prepend <string> (usually a directory
	including a trailing /)

--
	Do not interpret any more arguments as options.

Note that the order of the flags matters:

	checkout-cache -a -f file.c

will first check out all files listed in the cache (but not overwrite
any old ones), and then force-checkout file.c a second time (ie that
one _will_ overwrite any old contents with the same filename).

Also, just doing "checkout-cache" does nothing. You probably meant
"checkout-cache -a". And if you want to force it, you want
"checkout-cache -f -a".

Intuitiveness is not the goal here. Repeatability is. The reason for
the "no arguments means no work" thing is that from scripts you are
supposed to be able to do things like

	find . -name '*.h' -print0 | xargs -0 checkout-cache -f --

which will force all existing *.h files to be replaced with their
cached copies. If an empty command line implied "all", then this would
force-refresh everything in the cache, which was not the point.

To update and refresh only the files already checked out:

   checkout-cache -n -f -a && update-cache --ignore-missing --refresh

Oh, and the "--" is just a good idea when you know the rest will be
filenames. Just so that you wouldn't have a filename of "-a" causing
problems (not possible in the above example, but get used to it in
scripting!).

The prefix ability basically makes it trivial to use checkout-cache as
a "export as tree" function. Just read the desired tree into the
index, and do a
  
        checkout-cache --prefix=export-dir/ -a
  
and checkout-cache will "export" the cache into the specified
directory.
  
NOTE! The final "/" is important. The exported name is literally just
prefixed with the specified string, so you can also do something like
  
        checkout-cache --prefix=.merged- Makefile
  
to check out the currently cached copy of "Makefile" into the file
".merged-Makefile".


################################################################
commit-tree
	commit-tree <tree> [-p <parent commit>]*   < changelog

Creates a new commit object based on the provided tree object and
emits the new commit object id on stdout. If no parent is given then
it is considered to be an initial tree.

A commit object usually has 1 parent (a commit after a change) or up
to 16 parents.  More than one parent represents a merge of branches
that led to them.

While a tree represents a particular directory state of a working
directory, a commit represents that state in "time", and explains how
to get there.

Normally a commit would identify a new "HEAD" state, and while git
doesn't care where you save the note about that state, in practice we
tend to just write the result to the file ".git/HEAD", so that we can
always see what the last committed state was.

Options

<tree>
	An existing tree object

-p <parent commit>
	Each -p indicates a the id of a parent commit object.
	

Commit Information

A commit encapsulates:
	all parent object ids
	author name, email and date
	committer name and email and the commit time.

If not provided, commit-tree uses your name, hostname and domain to
provide author and committer info. This can be overridden using the
following environment variables.
	AUTHOR_NAME
	AUTHOR_EMAIL
	AUTHOR_DATE
	COMMIT_AUTHOR_NAME
	COMMIT_AUTHOR_EMAIL
(nb <,> and '\n's are stripped)

A commit comment is read from stdin (max 999 chars). If a changelog
entry is not provided via '<' redirection, commit-tree will just wait
for one to be entered and terminated with ^D

see also: write-tree


################################################################
diff-cache
	diff-cache [-p] [-r] [-z] [--cached] <tree/commit>

Compares the content and mode of the blobs found via a tree object
with the content of the current cache and, optionally ignoring the
stat state of the file on disk.

<tree/commit>
	The id of a tree or commit object to diff against.

-p
	generate patch (see section on generating patches)

-r
	recurse

-z
	\0 line termination on output

--cached
	do not consider the on-disk file at all

Output format:

See "Output format from diff-cache, diff-tree and show-diff" section.

Operating Modes

You can choose whether you want to trust the index file entirely
(using the "--cached" flag) or ask the diff logic to show any files
that don't match the stat state as being "tentatively changed".  Both
of these operations are very useful indeed.

Cached Mode

If --cached is specified, it allows you to ask:
	show me the differences between HEAD and the current index
	contents (the ones I'd write with a "write-tree")

For example, let's say that you have worked on your index file, and are
ready to commit. You want to see eactly _what_ you are going to commit is
without having to write a new tree object and compare it that way, and to
do that, you just do

	diff-cache --cached $(cat .git/HEAD)

Example: let's say I had renamed "commit.c" to "git-commit.c", and I had 
done an "upate-cache" to make that effective in the index file. 
"show-diff" wouldn't show anything at all, since the index file matches 
my working directory. But doing a diff-cache does:
	torvalds@ppc970:~/git> diff-cache --cached $(cat .git/HEAD)
	-100644 blob    4161aecc6700a2eb579e842af0b7f22b98443f74        commit.c
	+100644 blob    4161aecc6700a2eb579e842af0b7f22b98443f74        git-commit.c

And as you can see, the output matches "diff-tree -r" output (we
always do equivalent of "-r", since the index is flat).
You can trivially see that the above is a rename.

In fact, "diff-cache --cached" _should_ always be entirely equivalent to
actually doing a "write-tree" and comparing that. Except this one is much
nicer for the case where you just want to check where you are.

So doing a "diff-cache --cached" is basically very useful when you are 
asking yourself "what have I already marked for being committed, and 
what's the difference to a previous tree".

Non-cached Mode

The "non-cached" mode takes a different approach, and is potentially
the even more useful of the two in that what it does can't be emulated
with a "write-tree + diff-tree". Thus that's the default mode.  The
non-cached version asks the question

   "show me the differences between HEAD and the currently checked out 
    tree - index contents _and_ files that aren't up-to-date"

which is obviously a very useful question too, since that tells you what
you _could_ commit. Again, the output matches the "diff-tree -r" output to
a tee, but with a twist.

The twist is that if some file doesn't match the cache, we don't have a
backing store thing for it, and we use the magic "all-zero" sha1 to show
that. So let's say that you have edited "kernel/sched.c", but have not
actually done an update-cache on it yet - there is no "object" associated
with the new state, and you get:

	torvalds@ppc970:~/v2.6/linux> diff-cache $(cat .git/HEAD )
	*100644->100664 blob    7476bbcfe5ef5a1dd87d745f298b831143e4d77e->0000000000000000000000000000000000000000      kernel/sched.c

ie it shows that the tree has changed, and that "kernel/sched.c" has is
not up-to-date and may contain new stuff. The all-zero sha1 means that to
get the real diff, you need to look at the object in the working directory
directly rather than do an object-to-object diff.

NOTE! As with other commands of this type, "diff-cache" does not actually 
look at the contents of the file at all. So maybe "kernel/sched.c" hasn't 
actually changed, and it's just that you touched it. In either case, it's 
a note that you need to upate-cache it to make the cache be in sync.

NOTE 2! You can have a mixture of files show up as "has been updated" and
"is still dirty in the working directory" together. You can always tell
which file is in which state, since the "has been updated" ones show a
valid sha1, and the "not in sync with the index" ones will always have the
special all-zero sha1.

################################################################
diff-tree
	diff-tree [-p] [-r] [-z] <tree/commit> <tree/commit> [<pattern>]*

Compares the content and mode of the blobs found via two tree objects.

Note that diff-tree can use the tree encapsulated in a commit object.

<tree sha1>
	The id of a tree or commit object.

<pattern>

	If provided, the results are limited to a subset of files
	matching one of these prefix strings.
	ie file matches /^<pattern1>|<pattern2>|.../
	Note that pattern does not provide any wildcard or regexp features.

-p
	generate patch (see section on generating patches)

-r
	recurse

-z
	\0 line termination on output

Limiting Output

If you're only interested in differences in a subset of files, for
example some architecture-specific files, you might do:

	diff-tree -r <tree/commit> <tree/commit> arch/ia64 include/asm-ia64

and it will only show you what changed in those two directories.

Or if you are searching for what changed in just kernel/sched.c, just do

	diff-tree -r <tree/commit> <tree/commit> kernel/sched.c

and it will ignore all differences to other files.

The pattern is always the prefix, and is matched exactly (ie there are no
wildcards - although matching a directory, which it does support, can
obviously be seen as a "wildcard" for all the files under that directory).

Output format:

See "Output format from diff-cache, diff-tree and show-diff" section.

An example of normal usage is:

	torvalds@ppc970:~/git> diff-tree 5319e4d609cdd282069cc4dce33c1db559539b03 b4e628ea30d5ab3606119d2ea5caeab141d38df7
	*100664->100664 blob    ac348b7d5278e9d04e3a1cd417389379c32b014f->a01513ed4d4d565911a60981bfb4173311ba3688      fsck-cache.c

which tells you that the last commit changed just one file (it's from
this one:

	commit 3c6f7ca19ad4043e9e72fa94106f352897e651a8
	tree 5319e4d609cdd282069cc4dce33c1db559539b03
	parent b4e628ea30d5ab3606119d2ea5caeab141d38df7
	author Linus Torvalds <torvalds@ppc970.osdl.org> Sat Apr 9 12:02:30 2005
	committer Linus Torvalds <torvalds@ppc970.osdl.org> Sat Apr 9 12:02:30 2005

	Make "fsck-cache" print out all the root commits it finds.

	Once I do the reference tracking, I'll also make it print out all the
	HEAD commits it finds, which is even more interesting.

in case you care).

################################################################
diff-tree-helper
	diff-tree-helper [-z]

Reads output from diff-cache, diff-tree and show-diff and
generates patch format output.

-z
	\0 line termination on input

See also the section on generating patches.

################################################################
fsck-cache
	fsck-cache [[--unreachable] <commit>*]

Verifies the connectivity and validity of the objects in the database.

<commit>
	A commit object to treat as the head of an unreachability
	trace

--unreachable
	print out objects that exist but that aren't readable from any
	of the specified root nodes

It tests SHA1 and general object sanity, but it does full tracking of
the resulting reachability and everything else. It prints out any
corruption it finds (missing or bad objects), and if you use the
"--unreachable" flag it will also print out objects that exist but
that aren't readable from any of the specified root nodes.

So for example

	fsck-cache --unreachable $(cat .git/HEAD)

or, for Cogito users:

	fsck-cache --unreachable $(cat .git/heads/*)

will do quite a _lot_ of verification on the tree. There are a few
extra validity tests to be added (make sure that tree objects are
sorted properly etc), but on the whole if "fsck-cache" is happy, you
do have a valid tree.

Any corrupt objects you will have to find in backups or other archives
(ie you can just remove them and do an "rsync" with some other site in
the hopes that somebody else has the object you have corrupted).

Of course, "valid tree" doesn't mean that it wasn't generated by some
evil person, and the end result might be crap. Git is a revision
tracking system, not a quality assurance system ;)

Extracted Diagnostics

expect dangling commits - potential heads - due to lack of head information
	You haven't specified any nodes as heads so it won't be
	possible to differentiate between un-parented commits and
	root nodes.

missing sha1 directory '<dir>'
	The directory holding the sha1 objects is missing.

unreachable <type> <object>
	The <type> object <object>, isn't actually referred to directly
	or indirectly in any of the trees or commits seen. This can
	mean that there's another root na SHA1_ode that you're not specifying
	or that the tree is corrupt. If you haven't missed a root node
	then you might as well delete unreachable nodes since they
	can't be used.

missing <type> <object>
	The <type> object <object>, is referred to but isn't present in
	the database.

dangling <type> <object>
	The <type> object <object>, is present in the database but never
	_directly_ used. A dangling commit could be a root node.

warning: fsck-cache: tree <tree> has full pathnames in it
	And it shouldn't...

sha1 mismatch <object>
	The database has an object who's sha1 doesn't match the
	database value.
	This indicates a ??serious?? data integrity problem.
	(note: this error occured during early git development when
	the database format changed.)

Environment Variables

SHA1_FILE_DIRECTORY
	used to specify the object database root (usually .git/objects)

################################################################
git-export
	git-export top [base]

probably deprecated:
On Wed, 20 Apr 2005, Petr Baudis wrote:
>> I will probably not buy git-export, though. (That is, it is merged, but
>> I won't make git frontend for it.) My "git export" already does
>> something different, but more importantly, "git patch" of mine already
>> does effectively the same thing as you do, just for a single patch; so I
>> will probably just extend it to do it for an (a,b] range of patches.


That's fine. It was a quick hack, just to show that if somebody wants to, 
the data is trivially exportable.

		Linus

Although in Linus' distribution, git-export is not part of 'core' git.

################################################################
init-db
	init-db

This simply creates an empty git object database - basically a .git
directory.

If the object storage directory is specified via the
SHA1_FILE_DIRECTORY environment variable then the sha1 directories are
created underneath - otherwise the default .git/objects directory is
used.

init-db won't hurt an existing repository.


################################################################
ls-tree
	ls-tree [-r] [-z] <tree/commit>

convert the tree object to a human readable (and script
processable) form.

<tree/commit>
	Id of a tree or commit object.
-r
	recurse into sub-trees

-z
	\0 line termination on output

Output Format
<mode>\t	<type>\t	<object>\t	<path><file>	


################################################################
merge-base
	merge-base <commit> <commit>

merge-base finds as good a common ancestor as possible. Given a
selection of equally good common ancestors it should not be relied on
to decide in any particular way.

The merge-base algorithm is still in flux - use the source...


################################################################
merge-cache
	merge-cache <merge-program> (-a | -- | <file>*) 

This looks up the <file>(s) in the cache and, if there are any merge
entries, unpacks all of them (which may be just one file, of course)
into up to three separate temporary files, and then executes the
supplied <merge-program> with those three files as arguments 1,2,3
(empty argument if no file), and <file> as argument 4.

--
	Interpret all future arguments as filenames

-a
	Run merge against all files in the cache that need merging.

If merge-cache is called with multiple <file>s (or -a) then it
processes them in turn only stopping if merge returns a non-zero exit
code.

Typically this is run with the a script calling the merge command from
the RCS package.

A sample script called git-merge-one-file-script is included in the
ditribution.

ALERT ALERT ALERT! The git "merge object order" is different from the
RCS "merge" program merge object order. In the above ordering, the
original is first. But the argument order to the 3-way merge program
"merge" is to have the original in the middle. Don't ask me why.

Examples:

	torvalds@ppc970:~/merge-test> merge-cache cat MM
	This is MM from the original tree.			# original
	This is modified MM in the branch A.			# merge1
	This is modified MM in the branch B.			# merge2
	This is modified MM in the branch B.			# current contents

or 

	torvalds@ppc970:~/merge-test> merge-cache cat AA MM
	cat: : No such file or directory
	This is added AA in the branch A.
	This is added AA in the branch B.
	This is added AA in the branch B.
	fatal: merge program failed

where the latter example shows how "merge-cache" will stop trying to
merge once anything has returned an error (ie "cat" returned an error
for the AA file, because it didn't exist in the original, and thus
"merge-cache" didn't even try to merge the MM thing).


################################################################
read-tree
	read-tree (<tree/commit> | -m <tree/commit1> [<tree/commit2> <tree/commit3>])"

Reads the tree information given by <tree> into the directory cache,
but does not actually _update_ any of the files it "caches". (see:
checkout-cache)

Optionally, it can merge a tree into the cache or perform a 3-way
merge.

Trivial merges are done by read-tree itself.  Only conflicting paths
will be in unmerged state when read-tree returns.

-m
	Perform a merge, not just a read

<tree#>
	The id of the tree object(s) to be read/merged.


Merging
If -m is specified, read-tree performs 2 kinds of merge, a single tree
merge if only 1 tree is given or a 3-way merge if 3 trees are
provided.

Single Tree Merge
If only 1 tree is specified, read-tree operates as if the user did not
specify "-m", except that if the original cache has an entry for a
given pathname; and the contents of the path matches with the tree
being read, the stat info from the cache is used. (In other words, the
cache's stat()s take precedence over the merged tree's)

That means that if you do a "read-tree -m <newtree>" followed by a
"checkout-cache -f -a", the checkout-cache only checks out the stuff
that really changed.

This is used to avoid unnecessary false hits when show-diff is
run after read-tree.

3-Way Merge
Each "index" entry has two bits worth of "stage" state. stage 0 is the
normal one, and is the only one you'd see in any kind of normal use.

However, when you do "read-tree" with multiple trees, the "stage"
starts out at 0, but increments for each tree you read. And in
particular, the "-m" flag means "start at stage 1" instead.

This means that you can do

	read-tree -m <tree1> <tree2> <tree3>

and you will end up with an index with all of the <tree1> entries in
"stage1", all of the <tree2> entries in "stage2" and all of the
<tree3> entries in "stage3".

Furthermore, "read-tree" has special-case logic that says: if you see
a file that matches in all respects in the following states, it
"collapses" back to "stage0":

   - stage 2 and 3 are the same; take one or the other (it makes no
     difference - the same work has been done on stage 2 and 3)

   - stage 1 and stage 2 are the same and stage 3 is different; take
     stage 3 (some work has been done on stage 3)

   - stage 1 and stage 3 are the same and stage 2 is different take
     stage 2 (some work has been done on stage 2)

Write-tree refuses to write a nonsensical tree, so write-tree will
complain about unmerged entries if it sees a single entry that is not
stage 0".

Ok, this all sounds like a collection of totally nonsensical rules,
but it's actually exactly what you want in order to do a fast
merge. The different stages represent the "result tree" (stage 0, aka
"merged"), the original tree (stage 1, aka "orig"), and the two trees
you are trying to merge (stage 2 and 3 respectively).

In fact, the way "read-tree" works, it's entirely agnostic about how
you assign the stages, and you could really assign them any which way,
and the above is just a suggested way to do it (except since
"write-tree" refuses to write anything but stage0 entries, it makes
sense to always consider stage 0 to be the "full merge" state).

So what happens? Try it out. Select the original tree, and two trees
to merge, and look how it works:

 - if a file exists in identical format in all three trees, it will 
   automatically collapse to "merged" state by the new read-tree.

 - a file that has _any_ difference what-so-ever in the three trees
   will stay as separate entries in the index. It's up to "script
   policy" to determine how to remove the non-0 stages, and insert a
   merged version.  But since the index is always sorted, they're easy
   to find: they'll be clustered together.

 - the index file saves and restores with all this information, so you
   can merge things incrementally, but as long as it has entries in
   stages 1/2/3 (ie "unmerged entries") you can't write the result.

So now the merge algorithm ends up being really simple:

 - you walk the index in order, and ignore all entries of stage 0,
   since they've already been done.

 - if you find a "stage1", but no matching "stage2" or "stage3", you
   know it's been removed from both trees (it only existed in the
   original tree), and you remove that entry.  - if you find a
   matching "stage2" and "stage3" tree, you remove one of them, and
   turn the other into a "stage0" entry. Remove any matching "stage1"
   entry if it exists too.  .. all the normal trivial rules ..

Incidentally - it also means that you don't even have to have a separate 
subdirectory for this. All the information literally is in the index file, 
which is a temporary thing anyway. There is no need to worry about what is in 
the working directory, since it is never shown and never used.

see also:
write-tree
show-files


################################################################
rev-list <commit>

Lists commit objects in reverse chronological order starting at the
given commit, taking ancestry relationship into account.  This is
useful to produce human-readable log output.


################################################################
rev-tree
	rev-tree [--edges] [--cache <cache-file>] [^]<commit> [[^]<commit>]

Provides the revision tree for one or more commits.

--edges
	Show edges (ie places where the marking changes between parent
	and child)

--cache <cache-file>
	Use the specified file as a cache. [Not implemented yet]

[^]<commit>
	The commit id to trace (a leading caret means to ignore this
	commit-id and below)

Output:
<date> <commit>:<flags> [<parent-commit>:<flags> ]*

<date>
	Date in 'seconds since epoch'

<commit>
	id of commit object

<parent-commit>
	id of each parent commit object (>1 indicates a merge)

<flags>

	The flags are read as a bitmask representing each commit
	provided on the commandline. eg: given the command:

		 $ rev-tree <com1> <com2> <com3>

	The output:

	    <date> <commit>:5

	 means that <commit> is reachable from <com1>(1) and <com3>(4)
	
A revtree can get quite large. rev-tree will eventually allow you to
cache previous state so that you don't have to follow the whole thing
down.

So the change difference between two commits is literally

	rev-tree [commit-id1]  > commit1-revtree
	rev-tree [commit-id2]  > commit2-revtree
	join -t : commit1-revtree commit2-revtree > common-revisions

(this is also how to find the most common parent - you'd look at just
the head revisions - the ones that aren't referred to by other
revisions - in "common-revision", and figure out the best one. I
think.)


################################################################
show-diff
	show-diff [-p] [-q] [-s] [-z] [paths...]

Compares the files in the working tree and the cache.  When paths
are specified, compares only those named paths.  Otherwise all
entries in the cache are compared.  The output format is the
same as diff-cache and diff-tree.

-p
	generate patch (see section on generating patches)

-q
	Remain silent even on nonexisting files

-s
	Does not do anything other than what -q does.

Output format:

See "Output format from diff-cache, diff-tree and show-diff" section.

################################################################
show-files
	show-files [-z] [-t]
		(--[cached|deleted|others|ignored|stage|unmerged])*
		(-[c|d|o|i|s|u])*
		[-x <pattern>|--exclude=<pattern>]
		[-X <file>|--exclude-from=<file>]

This merges the file listing in the directory cache index with the
actual working directory list, and shows different combinations of the
two.

One or more of the options below may be used to determine the files
shown:

-c|--cached
	Show cached files in the output (default)

-d|--deleted
	Show deleted files in the output

-o|--others
	Show other files in the output

-i|--ignored
	Show ignored files in the output
	Note the this also reverses any exclude list present.

-s|--stage
	Show stage files in the output

-u|--unmerged
	Show unmerged files in the output (forces --stage)

#-t [not in Linus' tree (yet?)]
#	Identify the file status with the following tags (followed by
#	a space) at the start of each line:
#	H	cached
#	M	unmerged
#	R	removed/deleted
#	?	other

-z
	\0 line termination on output

-x|--exclude=<pattern>
	Skips files matching pattern.
	Note that pattern is a shell wildcard pattern.

-X|--exclude-from=<file>
	exclude patterns are read from <file>; 1 per line.
	Allows the use of the famous dontdiff file as follows to find
	out about uncommitted files just as dontdiff is used with
	the diff command:
	     show-files --others --exclude-from=dontdiff

Output
show files just outputs the filename unless --stage is specified in
which case it outputs:

[<tag> ]<mode> <object> <stage> <file>

show-files --unmerged" and "show-files --stage " can be used to examine
detailed information on unmerged paths.

For an unmerged path, instead of recording a single mode/SHA1 pair,
the dircache records up to three such pairs; one from tree O in stage
1, A in stage 2, and B in stage 3.  This information can be used by
the user (or Cogito) to see what should eventually be recorded at the
path. (see read-cache for more information on state)

see also:
read-cache


################################################################
unpack-file
	unpack-file <blob>

Creates a file holding the contents of the blob specified by sha1. It
returns the name of the temporary file in the following format:
	.merge_file_XXXXX

<blob>
	Must be a blob id

################################################################
update-cache
	update-cache [--add] [--remove] [--refresh [--ignore-missing]]
		     [--cacheinfo <mode> <object> <path>]*
		     [--] [<file>]*

Modifies the index or directory cache. Each file mentioned is updated
into the cache and any 'unmerged' or 'needs updating' state is
cleared.

The way update-cache handles files it is told about can be modified
using the various options:

--add
	If a specified file isn't in the cache already then it's
	added.
	Default behaviour is to ignore new files.

--remove
	If a specified file is in the cache but is missing then it's
	removed.
	Default behaviour is to ignore removed file.

--refresh
	Looks at the current cache and checks to see if merges or
	updates are needed by checking stat() information.

--ignore-missing
	Ignores missing files during a --refresh

--cacheinfo <mode> <object> <path>
	Directly insert the specified info into the cache.
	
--
	Do not interpret any more arguments as options.

<file>
	Files to act on.
	Note that files begining with '.' are discarded. This includes
	"./file" and "dir/./file". If you don't want this, then use	
	cleaner names.
	The same applies to directories ending '/' and paths with '//'


Using --refresh

--refresh does not calculate a new sha1 file or bring the cache
up-to-date for mode/content changes. But what it _does_ do is to
"re-match" the stat information of a file with the cache, so that you
can refresh the cache for a file that hasn't been changed but where
the stat entry is out of date.

For example, you'd want to do this after doing a "read-tree", to link
up the stat cache details with the proper files.

Using --cacheinfo
--cacheinfo is used to register a file that is not in the current
working directory.  This is useful for minimum-checkout merging.

To pretend you have a file with mode and sha1 at path, say:

 $ update-cache --cacheinfo mode sha1 path

To update and refresh only the files already checked out:

   checkout-cache -n -f -a && update-cache --ignore-missing --refresh


################################################################
write-tree
	write-tree

Creates a tree object using the current cache.

The cache must be merged.

Conceptually, write-tree sync()s the current directory cache contents
into a set of tree files.
In order to have that match what is actually in your directory right
now, you need to have done a "update-cache" phase before you did the
"write-tree".


################################################################

Output format from diff-cache, diff-tree and show-diff.

These commands all compare two sets of things; what are
compared are different:

    diff-cache <tree/commit>

        compares the <tree/commit> and the files on the filesystem.

    diff-cache --cached <tree/commit>

        compares the <tree/commit> and the cache.

    diff-tree [-r] <tree/commit-1> <tree/commit-2> [paths...]

        compares the trees named by the two arguments.

    show-diff [paths...]

        compares the cache and the files on the filesystem.

The following desription uses "old" and "new" to mean those
compared entities.

For files in old but not in new (i.e. removed):
-<mode> \t <type> \t <object> \t <path>

For files not in old but in new (i.e. added):
+<mode> \t <type> \t <object> \t <path>

For files that differ:
*<old-mode>-><new-mode> \t <type> \t <old-sha1>-><new-sha1> \t <path>

<new-sha1> is shown as all 0's if new is a file on the
filesystem and it is out of sync with the cache.  Example:

    *100644->100660 blob    5be4a414b32cf4204f889469942986d3d783da84->0000000000000000000000000000000000000000      file.c

################################################################

Generating patches

When diff-cache, diff-tree, or show-diff are run with a -p
option, they do not produce the output described in "Output
format from diff-cache, diff-tree and show-diff" section.  It
instead produces a patch file.

The patch generation can be customized at two levels.  This
customization also applies to diff-tree-helper.

1. When the environment variable GIT_EXTERNAL_DIFF is not set,
   these commands internally invoke diff like this:

   diff -L k/<path> -L l/<path> -pu <old> <new>

   For added files, /dev/null is used for <old>.  For removed
   files, /dev/null is used for <new>

   The first part of the above command-line can be customized via
   the environment variable GIT_DIFF_CMD.  For example, if you
   do not want to show the extra level of leading path, you can
   say this:

   GIT_DIFF_CMD="diff -L'%s' -L'%s'" show-diff -p

   Caution:  Do not use more than two '%s' in GIT_DIFF_CMD.

   The diff formatting options can be customized via the
   environment variable GIT_DIFF_OPTS.  For example, if you
   prefer context diff:

   GIT_DIFF_OPTS=-c diff-cache -p $(cat .git/HEAD)


2. When the environment variable GIT_EXTERNAL_DIFF is set, the
   program named by it is called, instead of the diff invocation
   described above.

   For a path that is added, removed, or modified,
   GIT_EXTERNAL_DIFF is called with 7 parameters:

     path old-file old-hex old-mode new-file new-hex new-mode

   where
     <old|new>-file are files GIT_EXTERNAL_DIFF can use to read the
                    contents of <old|ne>,
     <old|new>-hex are the 40-hexdigit SHA1 hashes,
     <old|new>-mode are the octal representation of the file modes.

   The file parameters can point at the user's working file
   (e.g. new-file in show-diff), /dev/null (e.g. old-file when a
   new file is added), or a temporary file (e.g. old-file in the
   cache).  GIT_EXTERNAL_DIFF should not worry about
   unlinking the temporary file --- it is removed when
   GIT_EXTERNAL_DIFF exits.

   For a path that is unmerged, GIT_EXTERNAL_DIFF is called with
   1 parameter, path.

################################################################

Terminology: - see README for description
Each line contains terms used interchangeably

object database, .git directory
directory cache, index
id, sha1, sha1-id, sha1 hash
type, tag
blob, blob object
tree, tree object
commit, commit object
parent
root object
changeset


git Environment Variables
AUTHOR_NAME
AUTHOR_EMAIL
AUTHOR_DATE
COMMIT_AUTHOR_NAME
COMMIT_AUTHOR_EMAIL
GIT_DIFF_CMD
GIT_DIFF_OPTS
GIT_EXTERNAL_DIFF
GIT_INDEX_FILE
SHA1_FILE_DIRECTORY

Re: Quick command reference

[Brian O'Mahoney]

Thank you both for taking the time and trouble to do this, particularly
with the name changes and new options; why don't you merge your efforts
and produce a GIT-Mini-HOWTO BTW send it off as a patch again!

regards, Brian

David Greaves wrote:
> Paul Mackerras wrote:
> 
> 
>>As an aid to my understanding of the core git commands, I created this
>>summary of the commands and their options and parameters.  I hope it
>>will be useful to others.  Corrections welcome of course.
>>
>>Paul.
>> 
>>
> 
> 
> Thanks Paul
> 
> Shame to see duplicated effort...
> 
> I've submitted this document to Linus and the list a few times and
> included all the feedback but for some reason it's not gone into any of
> the trees which means that people like you have to redo it from scratch...
> 
> Getting frustrated now...
> 
> David
> 
> 
> 
> ------------------------------------------------------------------------
> 
> This file contains reference information for the core git commands.
> It is actually based on the source from Petr Baudis' tree and may
> therefore contain a few 'extras' that may or may not make it upstream.
> 
> The README contains much useful definition and clarification info -
> read that first.  And of the commands, I suggest reading
> 'update-cache' and 'read-tree' first - I wish I had!
> 
> Thanks to original email authors and proof readers esp Junio C Hamano
> <junkio@cox.net>
> 
> David Greaves <david@dgreaves.com>
> 24/4/05
> 
> Identifier terminology used:
> 
> <object>
> 	Indicates any object sha1 identifier
> 
> <blob>
> 	Indicates a blob object sha1 identifier
> 
> <tree>
> 	Indicates a tree object sha1 identifier
> 
> <commit>
> 	Indicates a commit object sha1 identifier
> 
> <tree/commit>
> 	Indicates a tree or commit object sha1 identifier (usually
> 	because the command can read the <tree> a <commit> contains).
> 	[Eventually may be replaced with <tree> if <tree> means
> 	<tree/commit> in all commands]
> 
> <type>
> 	Indicates that an object type is required.
> 	Currently one of: blob/tree/commit
> 
> <file>
> 	Indicates a filename - often includes leading path
> 
> <path>
> 	Indicates the path of a file (is this ever useful?)
> 
> 
> 
> ################################################################
> cat-file
> 	cat-file (-t | <type>) <object>
> 
> Provide contents or type of objects in the repository. The type is
> required if -t is not being used to find the object type.
> 
> <object>
> 	The sha1 identifier of the object.
> 
> -t
> 	show the object type identified by <object>
> 
> <type>
> 	One of: blob/tree/commit
> 
> Output
> 
> If -t is specified, one of:
>         blob/tree/commit
> 
> Otherwise the raw (though uncompressed) contents of the <object> will
> be returned.
> 
> 
> ################################################################
> check-files
> 	check-files <file>...
> 
> Check that a list of files are up-to-date between the filesystem and
> the cache. Used to verify a patch target before doing a patch.
> 
> Files that do not exist on the filesystem are considered up-to-date
> (whether or not they are in the cache).
> 
> Emits an error message on failure.
> preparing to update existing file <file> not in cache
> 	  <file> exists but is not in the cache
> 
> preparing to update file <file> not uptodate in cache
> 	  <file> on disk is not up-to-date with the cache
> 
> exits with a status code indicating success if all files are
> up-to-date.
> 
> see also: update-cache
> 
> 
> ################################################################
> checkout-cache
> 	checkout-cache [-q] [-a] [-f] [-n] [--prefix=<string>]
> 		       [--] <file>...
> 
> Will copy all files listed from the cache to the working directory
> (not overwriting existing files). Note that the file contents are
> restored - NOT the file permissions.
> ??? l 58 checkout-cache.c says restore executable bit.
> 
> -q
> 	be quiet if files exist or are not in the cache
> 
> -f
> 	forces overwrite of existing files
> 
> -a
> 	checks out all files in the cache (will then continue to
> 	process listed files).
> -n
> 	Don't checkout new files, only refresh files already checked
> 	out.
> 
> --prefix=<string>
> 	When creating files, prepend <string> (usually a directory
> 	including a trailing /)
> 
> --
> 	Do not interpret any more arguments as options.
> 
> Note that the order of the flags matters:
> 
> 	checkout-cache -a -f file.c
> 
> will first check out all files listed in the cache (but not overwrite
> any old ones), and then force-checkout file.c a second time (ie that
> one _will_ overwrite any old contents with the same filename).
> 
> Also, just doing "checkout-cache" does nothing. You probably meant
> "checkout-cache -a". And if you want to force it, you want
> "checkout-cache -f -a".
> 
> Intuitiveness is not the goal here. Repeatability is. The reason for
> the "no arguments means no work" thing is that from scripts you are
> supposed to be able to do things like
> 
> 	find . -name '*.h' -print0 | xargs -0 checkout-cache -f --
> 
> which will force all existing *.h files to be replaced with their
> cached copies. If an empty command line implied "all", then this would
> force-refresh everything in the cache, which was not the point.
> 
> To update and refresh only the files already checked out:
> 
>    checkout-cache -n -f -a && update-cache --ignore-missing --refresh
> 
> Oh, and the "--" is just a good idea when you know the rest will be
> filenames. Just so that you wouldn't have a filename of "-a" causing
> problems (not possible in the above example, but get used to it in
> scripting!).
> 
> The prefix ability basically makes it trivial to use checkout-cache as
> a "export as tree" function. Just read the desired tree into the
> index, and do a
>   
>         checkout-cache --prefix=export-dir/ -a
>   
> and checkout-cache will "export" the cache into the specified
> directory.
>   
> NOTE! The final "/" is important. The exported name is literally just
> prefixed with the specified string, so you can also do something like
>   
>         checkout-cache --prefix=.merged- Makefile
>   
> to check out the currently cached copy of "Makefile" into the file
> ".merged-Makefile".
> 
> 
> ################################################################
> commit-tree
> 	commit-tree <tree> [-p <parent commit>]*   < changelog
> 
> Creates a new commit object based on the provided tree object and
> emits the new commit object id on stdout. If no parent is given then
> it is considered to be an initial tree.
> 
> A commit object usually has 1 parent (a commit after a change) or up
> to 16 parents.  More than one parent represents a merge of branches
> that led to them.
> 
> While a tree represents a particular directory state of a working
> directory, a commit represents that state in "time", and explains how
> to get there.
> 
> Normally a commit would identify a new "HEAD" state, and while git
> doesn't care where you save the note about that state, in practice we
> tend to just write the result to the file ".git/HEAD", so that we can
> always see what the last committed state was.
> 
> Options
> 
> <tree>
> 	An existing tree object
> 
> -p <parent commit>
> 	Each -p indicates a the id of a parent commit object.
> 	
> 
> Commit Information
> 
> A commit encapsulates:
> 	all parent object ids
> 	author name, email and date
> 	committer name and email and the commit time.
> 
> If not provided, commit-tree uses your name, hostname and domain to
> provide author and committer info. This can be overridden using the
> following environment variables.
> 	AUTHOR_NAME
> 	AUTHOR_EMAIL
> 	AUTHOR_DATE
> 	COMMIT_AUTHOR_NAME
> 	COMMIT_AUTHOR_EMAIL
> (nb <,> and '\n's are stripped)
> 
> A commit comment is read from stdin (max 999 chars). If a changelog
> entry is not provided via '<' redirection, commit-tree will just wait
> for one to be entered and terminated with ^D
> 
> see also: write-tree
> 
> 
> ################################################################
> diff-cache
> 	diff-cache [-p] [-r] [-z] [--cached] <tree/commit>
> 
> Compares the content and mode of the blobs found via a tree object
> with the content of the current cache and, optionally ignoring the
> stat state of the file on disk.
> 
> <tree/commit>
> 	The id of a tree or commit object to diff against.
> 
> -p
> 	generate patch (see section on generating patches)
> 
> -r
> 	recurse
> 
> -z
> 	\0 line termination on output
> 
> --cached
> 	do not consider the on-disk file at all
> 
> Output format:
> 
> See "Output format from diff-cache, diff-tree and show-diff" section.
> 
> Operating Modes
> 
> You can choose whether you want to trust the index file entirely
> (using the "--cached" flag) or ask the diff logic to show any files
> that don't match the stat state as being "tentatively changed".  Both
> of these operations are very useful indeed.
> 
> Cached Mode
> 
> If --cached is specified, it allows you to ask:
> 	show me the differences between HEAD and the current index
> 	contents (the ones I'd write with a "write-tree")
> 
> For example, let's say that you have worked on your index file, and are
> ready to commit. You want to see eactly _what_ you are going to commit is
> without having to write a new tree object and compare it that way, and to
> do that, you just do
> 
> 	diff-cache --cached $(cat .git/HEAD)
> 
> Example: let's say I had renamed "commit.c" to "git-commit.c", and I had 
> done an "upate-cache" to make that effective in the index file. 
> "show-diff" wouldn't show anything at all, since the index file matches 
> my working directory. But doing a diff-cache does:
> 	torvalds@ppc970:~/git> diff-cache --cached $(cat .git/HEAD)
> 	-100644 blob    4161aecc6700a2eb579e842af0b7f22b98443f74        commit.c
> 	+100644 blob    4161aecc6700a2eb579e842af0b7f22b98443f74        git-commit.c
> 
> And as you can see, the output matches "diff-tree -r" output (we
> always do equivalent of "-r", since the index is flat).
> You can trivially see that the above is a rename.
> 
> In fact, "diff-cache --cached" _should_ always be entirely equivalent to
> actually doing a "write-tree" and comparing that. Except this one is much
> nicer for the case where you just want to check where you are.
> 
> So doing a "diff-cache --cached" is basically very useful when you are 
> asking yourself "what have I already marked for being committed, and 
> what's the difference to a previous tree".
> 
> Non-cached Mode
> 
> The "non-cached" mode takes a different approach, and is potentially
> the even more useful of the two in that what it does can't be emulated
> with a "write-tree + diff-tree". Thus that's the default mode.  The
> non-cached version asks the question
> 
>    "show me the differences between HEAD and the currently checked out 
>     tree - index contents _and_ files that aren't up-to-date"
> 
> which is obviously a very useful question too, since that tells you what
> you _could_ commit. Again, the output matches the "diff-tree -r" output to
> a tee, but with a twist.
> 
> The twist is that if some file doesn't match the cache, we don't have a
> backing store thing for it, and we use the magic "all-zero" sha1 to show
> that. So let's say that you have edited "kernel/sched.c", but have not
> actually done an update-cache on it yet - there is no "object" associated
> with the new state, and you get:
> 
> 	torvalds@ppc970:~/v2.6/linux> diff-cache $(cat .git/HEAD )
> 	*100644->100664 blob    7476bbcfe5ef5a1dd87d745f298b831143e4d77e->0000000000000000000000000000000000000000      kernel/sched.c
> 
> ie it shows that the tree has changed, and that "kernel/sched.c" has is
> not up-to-date and may contain new stuff. The all-zero sha1 means that to
> get the real diff, you need to look at the object in the working directory
> directly rather than do an object-to-object diff.
> 
> NOTE! As with other commands of this type, "diff-cache" does not actually 
> look at the contents of the file at all. So maybe "kernel/sched.c" hasn't 
> actually changed, and it's just that you touched it. In either case, it's 
> a note that you need to upate-cache it to make the cache be in sync.
> 
> NOTE 2! You can have a mixture of files show up as "has been updated" and
> "is still dirty in the working directory" together. You can always tell
> which file is in which state, since the "has been updated" ones show a
> valid sha1, and the "not in sync with the index" ones will always have the
> special all-zero sha1.
> 
> ################################################################
> diff-tree
> 	diff-tree [-p] [-r] [-z] <tree/commit> <tree/commit> [<pattern>]*
> 
> Compares the content and mode of the blobs found via two tree objects.
> 
> Note that diff-tree can use the tree encapsulated in a commit object.
> 
> <tree sha1>
> 	The id of a tree or commit object.
> 
> <pattern>
> 
> 	If provided, the results are limited to a subset of files
> 	matching one of these prefix strings.
> 	ie file matches /^<pattern1>|<pattern2>|.../
> 	Note that pattern does not provide any wildcard or regexp features.
> 
> -p
> 	generate patch (see section on generating patches)
> 
> -r
> 	recurse
> 
> -z
> 	\0 line termination on output
> 
> Limiting Output
> 
> If you're only interested in differences in a subset of files, for
> example some architecture-specific files, you might do:
> 
> 	diff-tree -r <tree/commit> <tree/commit> arch/ia64 include/asm-ia64
> 
> and it will only show you what changed in those two directories.
> 
> Or if you are searching for what changed in just kernel/sched.c, just do
> 
> 	diff-tree -r <tree/commit> <tree/commit> kernel/sched.c
> 
> and it will ignore all differences to other files.
> 
> The pattern is always the prefix, and is matched exactly (ie there are no
> wildcards - although matching a directory, which it does support, can
> obviously be seen as a "wildcard" for all the files under that directory).
> 
> Output format:
> 
> See "Output format from diff-cache, diff-tree and show-diff" section.
> 
> An example of normal usage is:
> 
> 	torvalds@ppc970:~/git> diff-tree 5319e4d609cdd282069cc4dce33c1db559539b03 b4e628ea30d5ab3606119d2ea5caeab141d38df7
> 	*100664->100664 blob    ac348b7d5278e9d04e3a1cd417389379c32b014f->a01513ed4d4d565911a60981bfb4173311ba3688      fsck-cache.c
> 
> which tells you that the last commit changed just one file (it's from
> this one:
> 
> 	commit 3c6f7ca19ad4043e9e72fa94106f352897e651a8
> 	tree 5319e4d609cdd282069cc4dce33c1db559539b03
> 	parent b4e628ea30d5ab3606119d2ea5caeab141d38df7
> 	author Linus Torvalds <torvalds@ppc970.osdl.org> Sat Apr 9 12:02:30 2005
> 	committer Linus Torvalds <torvalds@ppc970.osdl.org> Sat Apr 9 12:02:30 2005
> 
> 	Make "fsck-cache" print out all the root commits it finds.
> 
> 	Once I do the reference tracking, I'll also make it print out all the
> 	HEAD commits it finds, which is even more interesting.
> 
> in case you care).
> 
> ################################################################
> diff-tree-helper
> 	diff-tree-helper [-z]
> 
> Reads output from diff-cache, diff-tree and show-diff and
> generates patch format output.
> 
> -z
> 	\0 line termination on input
> 
> See also the section on generating patches.
> 
> ################################################################
> fsck-cache
> 	fsck-cache [[--unreachable] <commit>*]
> 
> Verifies the connectivity and validity of the objects in the database.
> 
> <commit>
> 	A commit object to treat as the head of an unreachability
> 	trace
> 
> --unreachable
> 	print out objects that exist but that aren't readable from any
> 	of the specified root nodes
> 
> It tests SHA1 and general object sanity, but it does full tracking of
> the resulting reachability and everything else. It prints out any
> corruption it finds (missing or bad objects), and if you use the
> "--unreachable" flag it will also print out objects that exist but
> that aren't readable from any of the specified root nodes.
> 
> So for example
> 
> 	fsck-cache --unreachable $(cat .git/HEAD)
> 
> or, for Cogito users:
> 
> 	fsck-cache --unreachable $(cat .git/heads/*)
> 
> will do quite a _lot_ of verification on the tree. There are a few
> extra validity tests to be added (make sure that tree objects are
> sorted properly etc), but on the whole if "fsck-cache" is happy, you
> do have a valid tree.
> 
> Any corrupt objects you will have to find in backups or other archives
> (ie you can just remove them and do an "rsync" with some other site in
> the hopes that somebody else has the object you have corrupted).
> 
> Of course, "valid tree" doesn't mean that it wasn't generated by some
> evil person, and the end result might be crap. Git is a revision
> tracking system, not a quality assurance system ;)
> 
> Extracted Diagnostics
> 
> expect dangling commits - potential heads - due to lack of head information
> 	You haven't specified any nodes as heads so it won't be
> 	possible to differentiate between un-parented commits and
> 	root nodes.
> 
> missing sha1 directory '<dir>'
> 	The directory holding the sha1 objects is missing.
> 
> unreachable <type> <object>
> 	The <type> object <object>, isn't actually referred to directly
> 	or indirectly in any of the trees or commits seen. This can
> 	mean that there's another root na SHA1_ode that you're not specifying
> 	or that the tree is corrupt. If you haven't missed a root node
> 	then you might as well delete unreachable nodes since they
> 	can't be used.
> 
> missing <type> <object>
> 	The <type> object <object>, is referred to but isn't present in
> 	the database.
> 
> dangling <type> <object>
> 	The <type> object <object>, is present in the database but never
> 	_directly_ used. A dangling commit could be a root node.
> 
> warning: fsck-cache: tree <tree> has full pathnames in it
> 	And it shouldn't...
> 
> sha1 mismatch <object>
> 	The database has an object who's sha1 doesn't match the
> 	database value.
> 	This indicates a ??serious?? data integrity problem.
> 	(note: this error occured during early git development when
> 	the database format changed.)
> 
> Environment Variables
> 
> SHA1_FILE_DIRECTORY
> 	used to specify the object database root (usually .git/objects)
> 
> ################################################################
> git-export
> 	git-export top [base]
> 
> probably deprecated:
> On Wed, 20 Apr 2005, Petr Baudis wrote:
> 
>>>I will probably not buy git-export, though. (That is, it is merged, but
>>>I won't make git frontend for it.) My "git export" already does
>>>something different, but more importantly, "git patch" of mine already
>>>does effectively the same thing as you do, just for a single patch; so I
>>>will probably just extend it to do it for an (a,b] range of patches.
> 
> 
> 
> That's fine. It was a quick hack, just to show that if somebody wants to, 
> the data is trivially exportable.
> 
> 		Linus
> 
> Although in Linus' distribution, git-export is not part of 'core' git.
> 
> ################################################################
> init-db
> 	init-db
> 
> This simply creates an empty git object database - basically a .git
> directory.
> 
> If the object storage directory is specified via the
> SHA1_FILE_DIRECTORY environment variable then the sha1 directories are
> created underneath - otherwise the default .git/objects directory is
> used.
> 
> init-db won't hurt an existing repository.
> 
> 
> ################################################################
> ls-tree
> 	ls-tree [-r] [-z] <tree/commit>
> 
> convert the tree object to a human readable (and script
> processable) form.
> 
> <tree/commit>
> 	Id of a tree or commit object.
> -r
> 	recurse into sub-trees
> 
> -z
> 	\0 line termination on output
> 
> Output Format
> <mode>\t	<type>\t	<object>\t	<path><file>	
> 
> 
> ################################################################
> merge-base
> 	merge-base <commit> <commit>
> 
> merge-base finds as good a common ancestor as possible. Given a
> selection of equally good common ancestors it should not be relied on
> to decide in any particular way.
> 
> The merge-base algorithm is still in flux - use the source...
> 
> 
> ################################################################
> merge-cache
> 	merge-cache <merge-program> (-a | -- | <file>*) 
> 
> This looks up the <file>(s) in the cache and, if there are any merge
> entries, unpacks all of them (which may be just one file, of course)
> into up to three separate temporary files, and then executes the
> supplied <merge-program> with those three files as arguments 1,2,3
> (empty argument if no file), and <file> as argument 4.
> 
> --
> 	Interpret all future arguments as filenames
> 
> -a
> 	Run merge against all files in the cache that need merging.
> 
> If merge-cache is called with multiple <file>s (or -a) then it
> processes them in turn only stopping if merge returns a non-zero exit
> code.
> 
> Typically this is run with the a script calling the merge command from
> the RCS package.
> 
> A sample script called git-merge-one-file-script is included in the
> ditribution.
> 
> ALERT ALERT ALERT! The git "merge object order" is different from the
> RCS "merge" program merge object order. In the above ordering, the
> original is first. But the argument order to the 3-way merge program
> "merge" is to have the original in the middle. Don't ask me why.
> 
> Examples:
> 
> 	torvalds@ppc970:~/merge-test> merge-cache cat MM
> 	This is MM from the original tree.			# original
> 	This is modified MM in the branch A.			# merge1
> 	This is modified MM in the branch B.			# merge2
> 	This is modified MM in the branch B.			# current contents
> 
> or 
> 
> 	torvalds@ppc970:~/merge-test> merge-cache cat AA MM
> 	cat: : No such file or directory
> 	This is added AA in the branch A.
> 	This is added AA in the branch B.
> 	This is added AA in the branch B.
> 	fatal: merge program failed
> 
> where the latter example shows how "merge-cache" will stop trying to
> merge once anything has returned an error (ie "cat" returned an error
> for the AA file, because it didn't exist in the original, and thus
> "merge-cache" didn't even try to merge the MM thing).
> 
> 
> ################################################################
> read-tree
> 	read-tree (<tree/commit> | -m <tree/commit1> [<tree/commit2> <tree/commit3>])"
> 
> Reads the tree information given by <tree> into the directory cache,
> but does not actually _update_ any of the files it "caches". (see:
> checkout-cache)
> 
> Optionally, it can merge a tree into the cache or perform a 3-way
> merge.
> 
> Trivial merges are done by read-tree itself.  Only conflicting paths
> will be in unmerged state when read-tree returns.
> 
> -m
> 	Perform a merge, not just a read
> 
> <tree#>
> 	The id of the tree object(s) to be read/merged.
> 
> 
> Merging
> If -m is specified, read-tree performs 2 kinds of merge, a single tree
> merge if only 1 tree is given or a 3-way merge if 3 trees are
> provided.
> 
> Single Tree Merge
> If only 1 tree is specified, read-tree operates as if the user did not
> specify "-m", except that if the original cache has an entry for a
> given pathname; and the contents of the path matches with the tree
> being read, the stat info from the cache is used. (In other words, the
> cache's stat()s take precedence over the merged tree's)
> 
> That means that if you do a "read-tree -m <newtree>" followed by a
> "checkout-cache -f -a", the checkout-cache only checks out the stuff
> that really changed.
> 
> This is used to avoid unnecessary false hits when show-diff is
> run after read-tree.
> 
> 3-Way Merge
> Each "index" entry has two bits worth of "stage" state. stage 0 is the
> normal one, and is the only one you'd see in any kind of normal use.
> 
> However, when you do "read-tree" with multiple trees, the "stage"
> starts out at 0, but increments for each tree you read. And in
> particular, the "-m" flag means "start at stage 1" instead.
> 
> This means that you can do
> 
> 	read-tree -m <tree1> <tree2> <tree3>
> 
> and you will end up with an index with all of the <tree1> entries in
> "stage1", all of the <tree2> entries in "stage2" and all of the
> <tree3> entries in "stage3".
> 
> Furthermore, "read-tree" has special-case logic that says: if you see
> a file that matches in all respects in the following states, it
> "collapses" back to "stage0":
> 
>    - stage 2 and 3 are the same; take one or the other (it makes no
>      difference - the same work has been done on stage 2 and 3)
> 
>    - stage 1 and stage 2 are the same and stage 3 is different; take
>      stage 3 (some work has been done on stage 3)
> 
>    - stage 1 and stage 3 are the same and stage 2 is different take
>      stage 2 (some work has been done on stage 2)
> 
> Write-tree refuses to write a nonsensical tree, so write-tree will
> complain about unmerged entries if it sees a single entry that is not
> stage 0".
> 
> Ok, this all sounds like a collection of totally nonsensical rules,
> but it's actually exactly what you want in order to do a fast
> merge. The different stages represent the "result tree" (stage 0, aka
> "merged"), the original tree (stage 1, aka "orig"), and the two trees
> you are trying to merge (stage 2 and 3 respectively).
> 
> In fact, the way "read-tree" works, it's entirely agnostic about how
> you assign the stages, and you could really assign them any which way,
> and the above is just a suggested way to do it (except since
> "write-tree" refuses to write anything but stage0 entries, it makes
> sense to always consider stage 0 to be the "full merge" state).
> 
> So what happens? Try it out. Select the original tree, and two trees
> to merge, and look how it works:
> 
>  - if a file exists in identical format in all three trees, it will 
>    automatically collapse to "merged" state by the new read-tree.
> 
>  - a file that has _any_ difference what-so-ever in the three trees
>    will stay as separate entries in the index. It's up to "script
>    policy" to determine how to remove the non-0 stages, and insert a
>    merged version.  But since the index is always sorted, they're easy
>    to find: they'll be clustered together.
> 
>  - the index file saves and restores with all this information, so you
>    can merge things incrementally, but as long as it has entries in
>    stages 1/2/3 (ie "unmerged entries") you can't write the result.
> 
> So now the merge algorithm ends up being really simple:
> 
>  - you walk the index in order, and ignore all entries of stage 0,
>    since they've already been done.
> 
>  - if you find a "stage1", but no matching "stage2" or "stage3", you
>    know it's been removed from both trees (it only existed in the
>    original tree), and you remove that entry.  - if you find a
>    matching "stage2" and "stage3" tree, you remove one of them, and
>    turn the other into a "stage0" entry. Remove any matching "stage1"
>    entry if it exists too.  .. all the normal trivial rules ..
> 
> Incidentally - it also means that you don't even have to have a separate 
> subdirectory for this. All the information literally is in the index file, 
> which is a temporary thing anyway. There is no need to worry about what is in 
> the working directory, since it is never shown and never used.
> 
> see also:
> write-tree
> show-files
> 
> 
> ################################################################
> rev-list <commit>
> 
> Lists commit objects in reverse chronological order starting at the
> given commit, taking ancestry relationship into account.  This is
> useful to produce human-readable log output.
> 
> 
> ################################################################
> rev-tree
> 	rev-tree [--edges] [--cache <cache-file>] [^]<commit> [[^]<commit>]
> 
> Provides the revision tree for one or more commits.
> 
> --edges
> 	Show edges (ie places where the marking changes between parent
> 	and child)
> 
> --cache <cache-file>
> 	Use the specified file as a cache. [Not implemented yet]
> 
> [^]<commit>
> 	The commit id to trace (a leading caret means to ignore this
> 	commit-id and below)
> 
> Output:
> <date> <commit>:<flags> [<parent-commit>:<flags> ]*
> 
> <date>
> 	Date in 'seconds since epoch'
> 
> <commit>
> 	id of commit object
> 
> <parent-commit>
> 	id of each parent commit object (>1 indicates a merge)
> 
> <flags>
> 
> 	The flags are read as a bitmask representing each commit
> 	provided on the commandline. eg: given the command:
> 
> 		 $ rev-tree <com1> <com2> <com3>
> 
> 	The output:
> 
> 	    <date> <commit>:5
> 
> 	 means that <commit> is reachable from <com1>(1) and <com3>(4)
> 	
> A revtree can get quite large. rev-tree will eventually allow you to
> cache previous state so that you don't have to follow the whole thing
> down.
> 
> So the change difference between two commits is literally
> 
> 	rev-tree [commit-id1]  > commit1-revtree
> 	rev-tree [commit-id2]  > commit2-revtree
> 	join -t : commit1-revtree commit2-revtree > common-revisions
> 
> (this is also how to find the most common parent - you'd look at just
> the head revisions - the ones that aren't referred to by other
> revisions - in "common-revision", and figure out the best one. I
> think.)
> 
> 
> ################################################################
> show-diff
> 	show-diff [-p] [-q] [-s] [-z] [paths...]
> 
> Compares the files in the working tree and the cache.  When paths
> are specified, compares only those named paths.  Otherwise all
> entries in the cache are compared.  The output format is the
> same as diff-cache and diff-tree.
> 
> -p
> 	generate patch (see section on generating patches)
> 
> -q
> 	Remain silent even on nonexisting files
> 
> -s
> 	Does not do anything other than what -q does.
> 
> Output format:
> 
> See "Output format from diff-cache, diff-tree and show-diff" section.
> 
> ################################################################
> show-files
> 	show-files [-z] [-t]
> 		(--[cached|deleted|others|ignored|stage|unmerged])*
> 		(-[c|d|o|i|s|u])*
> 		[-x <pattern>|--exclude=<pattern>]
> 		[-X <file>|--exclude-from=<file>]
> 
> This merges the file listing in the directory cache index with the
> actual working directory list, and shows different combinations of the
> two.
> 
> One or more of the options below may be used to determine the files
> shown:
> 
> -c|--cached
> 	Show cached files in the output (default)
> 
> -d|--deleted
> 	Show deleted files in the output
> 
> -o|--others
> 	Show other files in the output
> 
> -i|--ignored
> 	Show ignored files in the output
> 	Note the this also reverses any exclude list present.
> 
> -s|--stage
> 	Show stage files in the output
> 
> -u|--unmerged
> 	Show unmerged files in the output (forces --stage)
> 
> #-t [not in Linus' tree (yet?)]
> #	Identify the file status with the following tags (followed by
> #	a space) at the start of each line:
> #	H	cached
> #	M	unmerged
> #	R	removed/deleted
> #	?	other
> 
> -z
> 	\0 line termination on output
> 
> -x|--exclude=<pattern>
> 	Skips files matching pattern.
> 	Note that pattern is a shell wildcard pattern.
> 
> -X|--exclude-from=<file>
> 	exclude patterns are read from <file>; 1 per line.
> 	Allows the use of the famous dontdiff file as follows to find
> 	out about uncommitted files just as dontdiff is used with
> 	the diff command:
> 	     show-files --others --exclude-from=dontdiff
> 
> Output
> show files just outputs the filename unless --stage is specified in
> which case it outputs:
> 
> [<tag> ]<mode> <object> <stage> <file>
> 
> show-files --unmerged" and "show-files --stage " can be used to examine
> detailed information on unmerged paths.
> 
> For an unmerged path, instead of recording a single mode/SHA1 pair,
> the dircache records up to three such pairs; one from tree O in stage
> 1, A in stage 2, and B in stage 3.  This information can be used by
> the user (or Cogito) to see what should eventually be recorded at the
> path. (see read-cache for more information on state)
> 
> see also:
> read-cache
> 
> 
> ################################################################
> unpack-file
> 	unpack-file <blob>
> 
> Creates a file holding the contents of the blob specified by sha1. It
> returns the name of the temporary file in the following format:
> 	.merge_file_XXXXX
> 
> <blob>
> 	Must be a blob id
> 
> ################################################################
> update-cache
> 	update-cache [--add] [--remove] [--refresh [--ignore-missing]]
> 		     [--cacheinfo <mode> <object> <path>]*
> 		     [--] [<file>]*
> 
> Modifies the index or directory cache. Each file mentioned is updated
> into the cache and any 'unmerged' or 'needs updating' state is
> cleared.
> 
> The way update-cache handles files it is told about can be modified
> using the various options:
> 
> --add
> 	If a specified file isn't in the cache already then it's
> 	added.
> 	Default behaviour is to ignore new files.
> 
> --remove
> 	If a specified file is in the cache but is missing then it's
> 	removed.
> 	Default behaviour is to ignore removed file.
> 
> --refresh
> 	Looks at the current cache and checks to see if merges or
> 	updates are needed by checking stat() information.
> 
> --ignore-missing
> 	Ignores missing files during a --refresh
> 
> --cacheinfo <mode> <object> <path>
> 	Directly insert the specified info into the cache.
> 	
> --
> 	Do not interpret any more arguments as options.
> 
> <file>
> 	Files to act on.
> 	Note that files begining with '.' are discarded. This includes
> 	"./file" and "dir/./file". If you don't want this, then use	
> 	cleaner names.
> 	The same applies to directories ending '/' and paths with '//'
> 
> 
> Using --refresh
> 
> --refresh does not calculate a new sha1 file or bring the cache
> up-to-date for mode/content changes. But what it _does_ do is to
> "re-match" the stat information of a file with the cache, so that you
> can refresh the cache for a file that hasn't been changed but where
> the stat entry is out of date.
> 
> For example, you'd want to do this after doing a "read-tree", to link
> up the stat cache details with the proper files.
> 
> Using --cacheinfo
> --cacheinfo is used to register a file that is not in the current
> working directory.  This is useful for minimum-checkout merging.
> 
> To pretend you have a file with mode and sha1 at path, say:
> 
>  $ update-cache --cacheinfo mode sha1 path
> 
> To update and refresh only the files already checked out:
> 
>    checkout-cache -n -f -a && update-cache --ignore-missing --refresh
> 
> 
> ################################################################
> write-tree
> 	write-tree
> 
> Creates a tree object using the current cache.
> 
> The cache must be merged.
> 
> Conceptually, write-tree sync()s the current directory cache contents
> into a set of tree files.
> In order to have that match what is actually in your directory right
> now, you need to have done a "update-cache" phase before you did the
> "write-tree".
> 
> 
> ################################################################
> 
> Output format from diff-cache, diff-tree and show-diff.
> 
> These commands all compare two sets of things; what are
> compared are different:
> 
>     diff-cache <tree/commit>
> 
>         compares the <tree/commit> and the files on the filesystem.
> 
>     diff-cache --cached <tree/commit>
> 
>         compares the <tree/commit> and the cache.
> 
>     diff-tree [-r] <tree/commit-1> <tree/commit-2> [paths...]
> 
>         compares the trees named by the two arguments.
> 
>     show-diff [paths...]
> 
>         compares the cache and the files on the filesystem.
> 
> The following desription uses "old" and "new" to mean those
> compared entities.
> 
> For files in old but not in new (i.e. removed):
> -<mode> \t <type> \t <object> \t <path>
> 
> For files not in old but in new (i.e. added):
> +<mode> \t <type> \t <object> \t <path>
> 
> For files that differ:
> *<old-mode>-><new-mode> \t <type> \t <old-sha1>-><new-sha1> \t <path>
> 
> <new-sha1> is shown as all 0's if new is a file on the
> filesystem and it is out of sync with the cache.  Example:
> 
>     *100644->100660 blob    5be4a414b32cf4204f889469942986d3d783da84->0000000000000000000000000000000000000000      file.c
> 
> ################################################################
> 
> Generating patches
> 
> When diff-cache, diff-tree, or show-diff are run with a -p
> option, they do not produce the output described in "Output
> format from diff-cache, diff-tree and show-diff" section.  It
> instead produces a patch file.
> 
> The patch generation can be customized at two levels.  This
> customization also applies to diff-tree-helper.
> 
> 1. When the environment variable GIT_EXTERNAL_DIFF is not set,
>    these commands internally invoke diff like this:
> 
>    diff -L k/<path> -L l/<path> -pu <old> <new>
> 
>    For added files, /dev/null is used for <old>.  For removed
>    files, /dev/null is used for <new>
> 
>    The first part of the above command-line can be customized via
>    the environment variable GIT_DIFF_CMD.  For example, if you
>    do not want to show the extra level of leading path, you can
>    say this:
> 
>    GIT_DIFF_CMD="diff -L'%s' -L'%s'" show-diff -p
> 
>    Caution:  Do not use more than two '%s' in GIT_DIFF_CMD.
> 
>    The diff formatting options can be customized via the
>    environment variable GIT_DIFF_OPTS.  For example, if you
>    prefer context diff:
> 
>    GIT_DIFF_OPTS=-c diff-cache -p $(cat .git/HEAD)
> 
> 
> 2. When the environment variable GIT_EXTERNAL_DIFF is set, the
>    program named by it is called, instead of the diff invocation
>    described above.
> 
>    For a path that is added, removed, or modified,
>    GIT_EXTERNAL_DIFF is called with 7 parameters:
> 
>      path old-file old-hex old-mode new-file new-hex new-mode
> 
>    where
>      <old|new>-file are files GIT_EXTERNAL_DIFF can use to read the
>                     contents of <old|ne>,
>      <old|new>-hex are the 40-hexdigit SHA1 hashes,
>      <old|new>-mode are the octal representation of the file modes.
> 
>    The file parameters can point at the user's working file
>    (e.g. new-file in show-diff), /dev/null (e.g. old-file when a
>    new file is added), or a temporary file (e.g. old-file in the
>    cache).  GIT_EXTERNAL_DIFF should not worry about
>    unlinking the temporary file --- it is removed when
>    GIT_EXTERNAL_DIFF exits.
> 
>    For a path that is unmerged, GIT_EXTERNAL_DIFF is called with
>    1 parameter, path.
> 
> ################################################################
> 
> Terminology: - see README for description
> Each line contains terms used interchangeably
> 
> object database, .git directory
> directory cache, index
> id, sha1, sha1-id, sha1 hash
> type, tag
> blob, blob object
> tree, tree object
> commit, commit object
> parent
> root object
> changeset
> 
> 
> git Environment Variables
> AUTHOR_NAME
> AUTHOR_EMAIL
> AUTHOR_DATE
> COMMIT_AUTHOR_NAME
> COMMIT_AUTHOR_EMAIL
> GIT_DIFF_CMD
> GIT_DIFF_OPTS
> GIT_EXTERNAL_DIFF
> GIT_INDEX_FILE
> SHA1_FILE_DIRECTORY
> 

-- 
mit freundlichen Grüßen, Brian.

Dr. Brian O'Mahoney
Mobile +41 (0)79 334 8035 Email: omb@bluewin.ch
Bleicherstrasse 25, CH-8953 Dietikon, Switzerland
PGP Key fingerprint = 33 41 A2 DE 35 7C CE 5D  F5 14 39 C9 6D 38 56 D5

Re: Quick command reference

[David Greaves]

Brian O'Mahoney wrote:

>Thank you both for taking the time and trouble to do this, particularly
>with the name changes and new options; why don't you merge your efforts
>and produce a GIT-Mini-HOWTO BTW send it off as a patch again!
>  
>
I will happily work on this as soon as Linus says that he'll accept it.
That way when people make changes to the options and behaviour of
commands they can trivially update the README.reference too.

Petr accepted an early version but then it became 'core git' rather than
Cogito so it made more sense to put it in Linus' tree.

I don't know if Linus just doesn't get my mails (ISPs?) or if he's not
bothered about docs right now? or he's plain busy?

I've spent many many hours doing this and I'm happy to spend many more -
but I'm at that frustrated point where it makes no sense until I know
it's of use.

Fingers crossed :)

David

Re: Quick command reference

[Linus Torvalds]

On Sun, 1 May 2005, David Greaves wrote:
> 
> I've spent many many hours doing this and I'm happy to spend many more -
> but I'm at that frustrated point where it makes no sense until I know
> it's of use.

I just tend to be concentrating on the technology itself, so docs 
invariably fall a bit behind for me, until I get to the point where I 
start looking at what (for me) ends up being the secondary things.

Anyway, what I'd really appreciate is a whole "Documentation" 
subdirectory, and preferably in some standard format. Maybe real 
old-fashioned man-pages, but hey, especially with something like this, 
just html would be good too.

(And no, by "standard format" I do _not_ mean xml or stuff like that. I 
mean something that is actually easy to read ;)

		Linus

Re: Quick command reference

[David Greaves]

[-- Attachment #1: Type: text/plain, Size: 2099 bytes --]

Linus Torvalds wrote:

>On Sun, 1 May 2005, David Greaves wrote:
>  
>
>>I've spent many many hours doing this and I'm happy to spend many more -
>>but I'm at that frustrated point where it makes no sense until I know
>>it's of use.
>>    
>>
>I just tend to be concentrating on the technology itself, so docs 
>invariably fall a bit behind for me, until I get to the point where I 
>start looking at what (for me) ends up being the secondary things.
>  
>
Yep - I expected as much. That's why _I_ did the README. Not sexy but
since I needed it, I figured others would...
And frankly I've been trying to balance badgering without being annoying
- but you keep saying what a thick skin you have so WTH, I kept on at it :)

>Anyway, what I'd really appreciate is a whole "Documentation" 
>subdirectory, and preferably in some standard format. Maybe real 
>old-fashioned man-pages, but hey, especially with something like this, 
>just html would be good too.
>  
>
That was the intent... it was supposed to look manpage-ish.
It's all in one file for now to make it easier to skip around and
cut'n'paste.
(Good job too since the command names still aren't stable.)

>(And no, by "standard format" I do _not_ mean xml or stuff like that. I 
>mean something that is actually easy to read ;)
>  
>
I chose text to start since it could easily be read on the mailing list.
I'll gladly put it into some kind of markup later when the features
start to stabilise.
For now people can wrap it in <pre> tags.

Please commit the version below (into a Documentation dir) and then all
I have to do is send you patches to commit and you don't have to put too
much effort into keeping it updated. It's 'only' docs - so although I
may get it wrong, people like Junio will be sure to correct me.

If you're OK with it then I can accept patches and track comments on the
list and act as collator/sub-editor. I can also do housekeeping like
keeping usage() strings consistent with the docs.

What say you?

David

Reference documentation for the core git commands.

Signed-off-by: David Greaves <david@dgreaves.com>

---



[-- Attachment #2: README.reference --]
[-- Type: text/plain, Size: 35927 bytes --]

This file contains reference information for the core git commands.
It is actually based on the source from Petr Baudis' tree and may
therefore contain a few 'extras' that may or may not make it upstream.

The README contains much useful definition and clarification info -
read that first.  And of the commands, I suggest reading
'update-cache' and 'read-tree' first - I wish I had!

Thanks to original email authors and proof readers esp Junio C Hamano
<junkio@cox.net>

David Greaves <david@dgreaves.com>
24/4/05

Identifier terminology used:

<object>
	Indicates any object sha1 identifier

<blob>
	Indicates a blob object sha1 identifier

<tree>
	Indicates a tree object sha1 identifier

<commit>
	Indicates a commit object sha1 identifier

<tree/commit>
	Indicates a tree or commit object sha1 identifier (usually
	because the command can read the <tree> a <commit> contains).
	[Eventually may be replaced with <tree> if <tree> means
	<tree/commit> in all commands]

<type>
	Indicates that an object type is required.
	Currently one of: blob/tree/commit

<file>
	Indicates a filename - often includes leading path

<path>
	Indicates the path of a file (is this ever useful?)



################################################################
cat-file
	cat-file (-t | <type>) <object>

Provide contents or type of objects in the repository. The type is
required if -t is not being used to find the object type.

<object>
	The sha1 identifier of the object.

-t
	show the object type identified by <object>

<type>
	One of: blob/tree/commit

Output

If -t is specified, one of:
        blob/tree/commit

Otherwise the raw (though uncompressed) contents of the <object> will
be returned.


################################################################
check-files
	check-files <file>...

Check that a list of files are up-to-date between the filesystem and
the cache. Used to verify a patch target before doing a patch.

Files that do not exist on the filesystem are considered up-to-date
(whether or not they are in the cache).

Emits an error message on failure.
preparing to update existing file <file> not in cache
	  <file> exists but is not in the cache

preparing to update file <file> not uptodate in cache
	  <file> on disk is not up-to-date with the cache

exits with a status code indicating success if all files are
up-to-date.

see also: update-cache


################################################################
checkout-cache
	checkout-cache [-q] [-a] [-f] [-n] [--prefix=<string>]
		       [--] <file>...

Will copy all files listed from the cache to the working directory
(not overwriting existing files). Note that the file contents are
restored - NOT the file permissions.
??? l 58 checkout-cache.c says restore executable bit.

-q
	be quiet if files exist or are not in the cache

-f
	forces overwrite of existing files

-a
	checks out all files in the cache (will then continue to
	process listed files).
-n
	Don't checkout new files, only refresh files already checked
	out.

--prefix=<string>
	When creating files, prepend <string> (usually a directory
	including a trailing /)

--
	Do not interpret any more arguments as options.

Note that the order of the flags matters:

	checkout-cache -a -f file.c

will first check out all files listed in the cache (but not overwrite
any old ones), and then force-checkout file.c a second time (ie that
one _will_ overwrite any old contents with the same filename).

Also, just doing "checkout-cache" does nothing. You probably meant
"checkout-cache -a". And if you want to force it, you want
"checkout-cache -f -a".

Intuitiveness is not the goal here. Repeatability is. The reason for
the "no arguments means no work" thing is that from scripts you are
supposed to be able to do things like

	find . -name '*.h' -print0 | xargs -0 checkout-cache -f --

which will force all existing *.h files to be replaced with their
cached copies. If an empty command line implied "all", then this would
force-refresh everything in the cache, which was not the point.

To update and refresh only the files already checked out:

   checkout-cache -n -f -a && update-cache --ignore-missing --refresh

Oh, and the "--" is just a good idea when you know the rest will be
filenames. Just so that you wouldn't have a filename of "-a" causing
problems (not possible in the above example, but get used to it in
scripting!).

The prefix ability basically makes it trivial to use checkout-cache as
a "export as tree" function. Just read the desired tree into the
index, and do a
  
        checkout-cache --prefix=export-dir/ -a
  
and checkout-cache will "export" the cache into the specified
directory.
  
NOTE! The final "/" is important. The exported name is literally just
prefixed with the specified string, so you can also do something like
  
        checkout-cache --prefix=.merged- Makefile
  
to check out the currently cached copy of "Makefile" into the file
".merged-Makefile".


################################################################
commit-tree
	commit-tree <tree> [-p <parent commit>]*   < changelog

Creates a new commit object based on the provided tree object and
emits the new commit object id on stdout. If no parent is given then
it is considered to be an initial tree.

A commit object usually has 1 parent (a commit after a change) or up
to 16 parents.  More than one parent represents a merge of branches
that led to them.

While a tree represents a particular directory state of a working
directory, a commit represents that state in "time", and explains how
to get there.

Normally a commit would identify a new "HEAD" state, and while git
doesn't care where you save the note about that state, in practice we
tend to just write the result to the file ".git/HEAD", so that we can
always see what the last committed state was.

Options

<tree>
	An existing tree object

-p <parent commit>
	Each -p indicates a the id of a parent commit object.
	

Commit Information

A commit encapsulates:
	all parent object ids
	author name, email and date
	committer name and email and the commit time.

If not provided, commit-tree uses your name, hostname and domain to
provide author and committer info. This can be overridden using the
following environment variables.
	AUTHOR_NAME
	AUTHOR_EMAIL
	AUTHOR_DATE
	COMMIT_AUTHOR_NAME
	COMMIT_AUTHOR_EMAIL
(nb <,> and '\n's are stripped)

A commit comment is read from stdin (max 999 chars). If a changelog
entry is not provided via '<' redirection, commit-tree will just wait
for one to be entered and terminated with ^D

see also: write-tree


################################################################
diff-cache
	diff-cache [-p] [-r] [-z] [--cached] <tree/commit>

Compares the content and mode of the blobs found via a tree object
with the content of the current cache and, optionally ignoring the
stat state of the file on disk.

<tree/commit>
	The id of a tree or commit object to diff against.

-p
	generate patch (see section on generating patches)

-r
	recurse

-z
	\0 line termination on output

--cached
	do not consider the on-disk file at all

Output format:

See "Output format from diff-cache, diff-tree and show-diff" section.

Operating Modes

You can choose whether you want to trust the index file entirely
(using the "--cached" flag) or ask the diff logic to show any files
that don't match the stat state as being "tentatively changed".  Both
of these operations are very useful indeed.

Cached Mode

If --cached is specified, it allows you to ask:
	show me the differences between HEAD and the current index
	contents (the ones I'd write with a "write-tree")

For example, let's say that you have worked on your index file, and are
ready to commit. You want to see eactly _what_ you are going to commit is
without having to write a new tree object and compare it that way, and to
do that, you just do

	diff-cache --cached $(cat .git/HEAD)

Example: let's say I had renamed "commit.c" to "git-commit.c", and I had 
done an "upate-cache" to make that effective in the index file. 
"show-diff" wouldn't show anything at all, since the index file matches 
my working directory. But doing a diff-cache does:
	torvalds@ppc970:~/git> diff-cache --cached $(cat .git/HEAD)
	-100644 blob    4161aecc6700a2eb579e842af0b7f22b98443f74        commit.c
	+100644 blob    4161aecc6700a2eb579e842af0b7f22b98443f74        git-commit.c

And as you can see, the output matches "diff-tree -r" output (we
always do equivalent of "-r", since the index is flat).
You can trivially see that the above is a rename.

In fact, "diff-cache --cached" _should_ always be entirely equivalent to
actually doing a "write-tree" and comparing that. Except this one is much
nicer for the case where you just want to check where you are.

So doing a "diff-cache --cached" is basically very useful when you are 
asking yourself "what have I already marked for being committed, and 
what's the difference to a previous tree".

Non-cached Mode

The "non-cached" mode takes a different approach, and is potentially
the even more useful of the two in that what it does can't be emulated
with a "write-tree + diff-tree". Thus that's the default mode.  The
non-cached version asks the question

   "show me the differences between HEAD and the currently checked out 
    tree - index contents _and_ files that aren't up-to-date"

which is obviously a very useful question too, since that tells you what
you _could_ commit. Again, the output matches the "diff-tree -r" output to
a tee, but with a twist.

The twist is that if some file doesn't match the cache, we don't have a
backing store thing for it, and we use the magic "all-zero" sha1 to show
that. So let's say that you have edited "kernel/sched.c", but have not
actually done an update-cache on it yet - there is no "object" associated
with the new state, and you get:

	torvalds@ppc970:~/v2.6/linux> diff-cache $(cat .git/HEAD )
	*100644->100664 blob    7476bbcfe5ef5a1dd87d745f298b831143e4d77e->0000000000000000000000000000000000000000      kernel/sched.c

ie it shows that the tree has changed, and that "kernel/sched.c" has is
not up-to-date and may contain new stuff. The all-zero sha1 means that to
get the real diff, you need to look at the object in the working directory
directly rather than do an object-to-object diff.

NOTE! As with other commands of this type, "diff-cache" does not actually 
look at the contents of the file at all. So maybe "kernel/sched.c" hasn't 
actually changed, and it's just that you touched it. In either case, it's 
a note that you need to upate-cache it to make the cache be in sync.

NOTE 2! You can have a mixture of files show up as "has been updated" and
"is still dirty in the working directory" together. You can always tell
which file is in which state, since the "has been updated" ones show a
valid sha1, and the "not in sync with the index" ones will always have the
special all-zero sha1.

################################################################
diff-tree
	diff-tree [-p] [-r] [-z] <tree/commit> <tree/commit> [<pattern>]*

Compares the content and mode of the blobs found via two tree objects.

Note that diff-tree can use the tree encapsulated in a commit object.

<tree sha1>
	The id of a tree or commit object.

<pattern>

	If provided, the results are limited to a subset of files
	matching one of these prefix strings.
	ie file matches /^<pattern1>|<pattern2>|.../
	Note that pattern does not provide any wildcard or regexp features.

-p
	generate patch (see section on generating patches)

-r
	recurse

-z
	\0 line termination on output

Limiting Output

If you're only interested in differences in a subset of files, for
example some architecture-specific files, you might do:

	diff-tree -r <tree/commit> <tree/commit> arch/ia64 include/asm-ia64

and it will only show you what changed in those two directories.

Or if you are searching for what changed in just kernel/sched.c, just do

	diff-tree -r <tree/commit> <tree/commit> kernel/sched.c

and it will ignore all differences to other files.

The pattern is always the prefix, and is matched exactly (ie there are no
wildcards - although matching a directory, which it does support, can
obviously be seen as a "wildcard" for all the files under that directory).

Output format:

See "Output format from diff-cache, diff-tree and show-diff" section.

An example of normal usage is:

	torvalds@ppc970:~/git> diff-tree 5319e4d609cdd282069cc4dce33c1db559539b03 b4e628ea30d5ab3606119d2ea5caeab141d38df7
	*100664->100664 blob    ac348b7d5278e9d04e3a1cd417389379c32b014f->a01513ed4d4d565911a60981bfb4173311ba3688      fsck-cache.c

which tells you that the last commit changed just one file (it's from
this one:

	commit 3c6f7ca19ad4043e9e72fa94106f352897e651a8
	tree 5319e4d609cdd282069cc4dce33c1db559539b03
	parent b4e628ea30d5ab3606119d2ea5caeab141d38df7
	author Linus Torvalds <torvalds@ppc970.osdl.org> Sat Apr 9 12:02:30 2005
	committer Linus Torvalds <torvalds@ppc970.osdl.org> Sat Apr 9 12:02:30 2005

	Make "fsck-cache" print out all the root commits it finds.

	Once I do the reference tracking, I'll also make it print out all the
	HEAD commits it finds, which is even more interesting.

in case you care).

################################################################
diff-tree-helper
	diff-tree-helper [-z]

Reads output from diff-cache, diff-tree and show-diff and
generates patch format output.

-z
	\0 line termination on input

See also the section on generating patches.

################################################################
fsck-cache
	fsck-cache [[--unreachable] <commit>*]

Verifies the connectivity and validity of the objects in the database.

<commit>
	A commit object to treat as the head of an unreachability
	trace

--unreachable
	print out objects that exist but that aren't readable from any
	of the specified root nodes

It tests SHA1 and general object sanity, but it does full tracking of
the resulting reachability and everything else. It prints out any
corruption it finds (missing or bad objects), and if you use the
"--unreachable" flag it will also print out objects that exist but
that aren't readable from any of the specified root nodes.

So for example

	fsck-cache --unreachable $(cat .git/HEAD)

or, for Cogito users:

	fsck-cache --unreachable $(cat .git/heads/*)

will do quite a _lot_ of verification on the tree. There are a few
extra validity tests to be added (make sure that tree objects are
sorted properly etc), but on the whole if "fsck-cache" is happy, you
do have a valid tree.

Any corrupt objects you will have to find in backups or other archives
(ie you can just remove them and do an "rsync" with some other site in
the hopes that somebody else has the object you have corrupted).

Of course, "valid tree" doesn't mean that it wasn't generated by some
evil person, and the end result might be crap. Git is a revision
tracking system, not a quality assurance system ;)

Extracted Diagnostics

expect dangling commits - potential heads - due to lack of head information
	You haven't specified any nodes as heads so it won't be
	possible to differentiate between un-parented commits and
	root nodes.

missing sha1 directory '<dir>'
	The directory holding the sha1 objects is missing.

unreachable <type> <object>
	The <type> object <object>, isn't actually referred to directly
	or indirectly in any of the trees or commits seen. This can
	mean that there's another root na SHA1_ode that you're not specifying
	or that the tree is corrupt. If you haven't missed a root node
	then you might as well delete unreachable nodes since they
	can't be used.

missing <type> <object>
	The <type> object <object>, is referred to but isn't present in
	the database.

dangling <type> <object>
	The <type> object <object>, is present in the database but never
	_directly_ used. A dangling commit could be a root node.

warning: fsck-cache: tree <tree> has full pathnames in it
	And it shouldn't...

sha1 mismatch <object>
	The database has an object who's sha1 doesn't match the
	database value.
	This indicates a ??serious?? data integrity problem.
	(note: this error occured during early git development when
	the database format changed.)

Environment Variables

SHA1_FILE_DIRECTORY
	used to specify the object database root (usually .git/objects)

################################################################
git-export
	git-export top [base]

probably deprecated:
On Wed, 20 Apr 2005, Petr Baudis wrote:
>> I will probably not buy git-export, though. (That is, it is merged, but
>> I won't make git frontend for it.) My "git export" already does
>> something different, but more importantly, "git patch" of mine already
>> does effectively the same thing as you do, just for a single patch; so I
>> will probably just extend it to do it for an (a,b] range of patches.


That's fine. It was a quick hack, just to show that if somebody wants to, 
the data is trivially exportable.

		Linus

Although in Linus' distribution, git-export is not part of 'core' git.

################################################################
init-db
	init-db

This simply creates an empty git object database - basically a .git
directory.

If the object storage directory is specified via the
SHA1_FILE_DIRECTORY environment variable then the sha1 directories are
created underneath - otherwise the default .git/objects directory is
used.

init-db won't hurt an existing repository.


################################################################
ls-tree
	ls-tree [-r] [-z] <tree/commit>

convert the tree object to a human readable (and script
processable) form.

<tree/commit>
	Id of a tree or commit object.
-r
	recurse into sub-trees

-z
	\0 line termination on output

Output Format
<mode>\t	<type>\t	<object>\t	<path><file>	


################################################################
merge-base
	merge-base <commit> <commit>

merge-base finds as good a common ancestor as possible. Given a
selection of equally good common ancestors it should not be relied on
to decide in any particular way.

The merge-base algorithm is still in flux - use the source...


################################################################
merge-cache
	merge-cache <merge-program> (-a | -- | <file>*) 

This looks up the <file>(s) in the cache and, if there are any merge
entries, unpacks all of them (which may be just one file, of course)
into up to three separate temporary files, and then executes the
supplied <merge-program> with those three files as arguments 1,2,3
(empty argument if no file), and <file> as argument 4.

--
	Interpret all future arguments as filenames

-a
	Run merge against all files in the cache that need merging.

If merge-cache is called with multiple <file>s (or -a) then it
processes them in turn only stopping if merge returns a non-zero exit
code.

Typically this is run with the a script calling the merge command from
the RCS package.

A sample script called git-merge-one-file-script is included in the
ditribution.

ALERT ALERT ALERT! The git "merge object order" is different from the
RCS "merge" program merge object order. In the above ordering, the
original is first. But the argument order to the 3-way merge program
"merge" is to have the original in the middle. Don't ask me why.

Examples:

	torvalds@ppc970:~/merge-test> merge-cache cat MM
	This is MM from the original tree.			# original
	This is modified MM in the branch A.			# merge1
	This is modified MM in the branch B.			# merge2
	This is modified MM in the branch B.			# current contents

or 

	torvalds@ppc970:~/merge-test> merge-cache cat AA MM
	cat: : No such file or directory
	This is added AA in the branch A.
	This is added AA in the branch B.
	This is added AA in the branch B.
	fatal: merge program failed

where the latter example shows how "merge-cache" will stop trying to
merge once anything has returned an error (ie "cat" returned an error
for the AA file, because it didn't exist in the original, and thus
"merge-cache" didn't even try to merge the MM thing).


################################################################
read-tree
	read-tree (<tree/commit> | -m <tree/commit1> [<tree/commit2> <tree/commit3>])"

Reads the tree information given by <tree> into the directory cache,
but does not actually _update_ any of the files it "caches". (see:
checkout-cache)

Optionally, it can merge a tree into the cache or perform a 3-way
merge.

Trivial merges are done by read-tree itself.  Only conflicting paths
will be in unmerged state when read-tree returns.

-m
	Perform a merge, not just a read

<tree#>
	The id of the tree object(s) to be read/merged.


Merging
If -m is specified, read-tree performs 2 kinds of merge, a single tree
merge if only 1 tree is given or a 3-way merge if 3 trees are
provided.

Single Tree Merge
If only 1 tree is specified, read-tree operates as if the user did not
specify "-m", except that if the original cache has an entry for a
given pathname; and the contents of the path matches with the tree
being read, the stat info from the cache is used. (In other words, the
cache's stat()s take precedence over the merged tree's)

That means that if you do a "read-tree -m <newtree>" followed by a
"checkout-cache -f -a", the checkout-cache only checks out the stuff
that really changed.

This is used to avoid unnecessary false hits when show-diff is
run after read-tree.

3-Way Merge
Each "index" entry has two bits worth of "stage" state. stage 0 is the
normal one, and is the only one you'd see in any kind of normal use.

However, when you do "read-tree" with multiple trees, the "stage"
starts out at 0, but increments for each tree you read. And in
particular, the "-m" flag means "start at stage 1" instead.

This means that you can do

	read-tree -m <tree1> <tree2> <tree3>

and you will end up with an index with all of the <tree1> entries in
"stage1", all of the <tree2> entries in "stage2" and all of the
<tree3> entries in "stage3".

Furthermore, "read-tree" has special-case logic that says: if you see
a file that matches in all respects in the following states, it
"collapses" back to "stage0":

   - stage 2 and 3 are the same; take one or the other (it makes no
     difference - the same work has been done on stage 2 and 3)

   - stage 1 and stage 2 are the same and stage 3 is different; take
     stage 3 (some work has been done on stage 3)

   - stage 1 and stage 3 are the same and stage 2 is different take
     stage 2 (some work has been done on stage 2)

Write-tree refuses to write a nonsensical tree, so write-tree will
complain about unmerged entries if it sees a single entry that is not
stage 0".

Ok, this all sounds like a collection of totally nonsensical rules,
but it's actually exactly what you want in order to do a fast
merge. The different stages represent the "result tree" (stage 0, aka
"merged"), the original tree (stage 1, aka "orig"), and the two trees
you are trying to merge (stage 2 and 3 respectively).

In fact, the way "read-tree" works, it's entirely agnostic about how
you assign the stages, and you could really assign them any which way,
and the above is just a suggested way to do it (except since
"write-tree" refuses to write anything but stage0 entries, it makes
sense to always consider stage 0 to be the "full merge" state).

So what happens? Try it out. Select the original tree, and two trees
to merge, and look how it works:

 - if a file exists in identical format in all three trees, it will 
   automatically collapse to "merged" state by the new read-tree.

 - a file that has _any_ difference what-so-ever in the three trees
   will stay as separate entries in the index. It's up to "script
   policy" to determine how to remove the non-0 stages, and insert a
   merged version.  But since the index is always sorted, they're easy
   to find: they'll be clustered together.

 - the index file saves and restores with all this information, so you
   can merge things incrementally, but as long as it has entries in
   stages 1/2/3 (ie "unmerged entries") you can't write the result.

So now the merge algorithm ends up being really simple:

 - you walk the index in order, and ignore all entries of stage 0,
   since they've already been done.

 - if you find a "stage1", but no matching "stage2" or "stage3", you
   know it's been removed from both trees (it only existed in the
   original tree), and you remove that entry.  - if you find a
   matching "stage2" and "stage3" tree, you remove one of them, and
   turn the other into a "stage0" entry. Remove any matching "stage1"
   entry if it exists too.  .. all the normal trivial rules ..

Incidentally - it also means that you don't even have to have a separate 
subdirectory for this. All the information literally is in the index file, 
which is a temporary thing anyway. There is no need to worry about what is in 
the working directory, since it is never shown and never used.

see also:
write-tree
show-files


################################################################
rev-list <commit>

Lists commit objects in reverse chronological order starting at the
given commit, taking ancestry relationship into account.  This is
useful to produce human-readable log output.


################################################################
rev-tree
	rev-tree [--edges] [--cache <cache-file>] [^]<commit> [[^]<commit>]

Provides the revision tree for one or more commits.

--edges
	Show edges (ie places where the marking changes between parent
	and child)

--cache <cache-file>
	Use the specified file as a cache. [Not implemented yet]

[^]<commit>
	The commit id to trace (a leading caret means to ignore this
	commit-id and below)

Output:
<date> <commit>:<flags> [<parent-commit>:<flags> ]*

<date>
	Date in 'seconds since epoch'

<commit>
	id of commit object

<parent-commit>
	id of each parent commit object (>1 indicates a merge)

<flags>

	The flags are read as a bitmask representing each commit
	provided on the commandline. eg: given the command:

		 $ rev-tree <com1> <com2> <com3>

	The output:

	    <date> <commit>:5

	 means that <commit> is reachable from <com1>(1) and <com3>(4)
	
A revtree can get quite large. rev-tree will eventually allow you to
cache previous state so that you don't have to follow the whole thing
down.

So the change difference between two commits is literally

	rev-tree [commit-id1]  > commit1-revtree
	rev-tree [commit-id2]  > commit2-revtree
	join -t : commit1-revtree commit2-revtree > common-revisions

(this is also how to find the most common parent - you'd look at just
the head revisions - the ones that aren't referred to by other
revisions - in "common-revision", and figure out the best one. I
think.)


################################################################
show-diff
	show-diff [-p] [-q] [-s] [-z] [paths...]

Compares the files in the working tree and the cache.  When paths
are specified, compares only those named paths.  Otherwise all
entries in the cache are compared.  The output format is the
same as diff-cache and diff-tree.

-p
	generate patch (see section on generating patches)

-q
	Remain silent even on nonexisting files

-s
	Does not do anything other than what -q does.

Output format:

See "Output format from diff-cache, diff-tree and show-diff" section.

################################################################
show-files
	show-files [-z] [-t]
		(--[cached|deleted|others|ignored|stage|unmerged])*
		(-[c|d|o|i|s|u])*
		[-x <pattern>|--exclude=<pattern>]
		[-X <file>|--exclude-from=<file>]

This merges the file listing in the directory cache index with the
actual working directory list, and shows different combinations of the
two.

One or more of the options below may be used to determine the files
shown:

-c|--cached
	Show cached files in the output (default)

-d|--deleted
	Show deleted files in the output

-o|--others
	Show other files in the output

-i|--ignored
	Show ignored files in the output
	Note the this also reverses any exclude list present.

-s|--stage
	Show stage files in the output

-u|--unmerged
	Show unmerged files in the output (forces --stage)

#-t [not in Linus' tree (yet?)]
#	Identify the file status with the following tags (followed by
#	a space) at the start of each line:
#	H	cached
#	M	unmerged
#	R	removed/deleted
#	?	other

-z
	\0 line termination on output

-x|--exclude=<pattern>
	Skips files matching pattern.
	Note that pattern is a shell wildcard pattern.

-X|--exclude-from=<file>
	exclude patterns are read from <file>; 1 per line.
	Allows the use of the famous dontdiff file as follows to find
	out about uncommitted files just as dontdiff is used with
	the diff command:
	     show-files --others --exclude-from=dontdiff

Output
show files just outputs the filename unless --stage is specified in
which case it outputs:

[<tag> ]<mode> <object> <stage> <file>

show-files --unmerged" and "show-files --stage " can be used to examine
detailed information on unmerged paths.

For an unmerged path, instead of recording a single mode/SHA1 pair,
the dircache records up to three such pairs; one from tree O in stage
1, A in stage 2, and B in stage 3.  This information can be used by
the user (or Cogito) to see what should eventually be recorded at the
path. (see read-cache for more information on state)

see also:
read-cache


################################################################
unpack-file
	unpack-file <blob>

Creates a file holding the contents of the blob specified by sha1. It
returns the name of the temporary file in the following format:
	.merge_file_XXXXX

<blob>
	Must be a blob id

################################################################
update-cache
	update-cache [--add] [--remove] [--refresh [--ignore-missing]]
		     [--cacheinfo <mode> <object> <path>]*
		     [--] [<file>]*

Modifies the index or directory cache. Each file mentioned is updated
into the cache and any 'unmerged' or 'needs updating' state is
cleared.

The way update-cache handles files it is told about can be modified
using the various options:

--add
	If a specified file isn't in the cache already then it's
	added.
	Default behaviour is to ignore new files.

--remove
	If a specified file is in the cache but is missing then it's
	removed.
	Default behaviour is to ignore removed file.

--refresh
	Looks at the current cache and checks to see if merges or
	updates are needed by checking stat() information.

--ignore-missing
	Ignores missing files during a --refresh

--cacheinfo <mode> <object> <path>
	Directly insert the specified info into the cache.
	
--
	Do not interpret any more arguments as options.

<file>
	Files to act on.
	Note that files begining with '.' are discarded. This includes
	"./file" and "dir/./file". If you don't want this, then use	
	cleaner names.
	The same applies to directories ending '/' and paths with '//'


Using --refresh

--refresh does not calculate a new sha1 file or bring the cache
up-to-date for mode/content changes. But what it _does_ do is to
"re-match" the stat information of a file with the cache, so that you
can refresh the cache for a file that hasn't been changed but where
the stat entry is out of date.

For example, you'd want to do this after doing a "read-tree", to link
up the stat cache details with the proper files.

Using --cacheinfo
--cacheinfo is used to register a file that is not in the current
working directory.  This is useful for minimum-checkout merging.

To pretend you have a file with mode and sha1 at path, say:

 $ update-cache --cacheinfo mode sha1 path

To update and refresh only the files already checked out:

   checkout-cache -n -f -a && update-cache --ignore-missing --refresh


################################################################
write-tree
	write-tree

Creates a tree object using the current cache.

The cache must be merged.

Conceptually, write-tree sync()s the current directory cache contents
into a set of tree files.
In order to have that match what is actually in your directory right
now, you need to have done a "update-cache" phase before you did the
"write-tree".


################################################################

Output format from diff-cache, diff-tree and show-diff.

These commands all compare two sets of things; what are
compared are different:

    diff-cache <tree/commit>

        compares the <tree/commit> and the files on the filesystem.

    diff-cache --cached <tree/commit>

        compares the <tree/commit> and the cache.

    diff-tree [-r] <tree/commit-1> <tree/commit-2> [paths...]

        compares the trees named by the two arguments.

    show-diff [paths...]

        compares the cache and the files on the filesystem.

The following desription uses "old" and "new" to mean those
compared entities.

For files in old but not in new (i.e. removed):
-<mode> \t <type> \t <object> \t <path>

For files not in old but in new (i.e. added):
+<mode> \t <type> \t <object> \t <path>

For files that differ:
*<old-mode>-><new-mode> \t <type> \t <old-sha1>-><new-sha1> \t <path>

<new-sha1> is shown as all 0's if new is a file on the
filesystem and it is out of sync with the cache.  Example:

    *100644->100660 blob    5be4a414b32cf4204f889469942986d3d783da84->0000000000000000000000000000000000000000      file.c

################################################################

Generating patches

When diff-cache, diff-tree, or show-diff are run with a -p
option, they do not produce the output described in "Output
format from diff-cache, diff-tree and show-diff" section.  It
instead produces a patch file.

The patch generation can be customized at two levels.  This
customization also applies to diff-tree-helper.

1. When the environment variable GIT_EXTERNAL_DIFF is not set,
   these commands internally invoke diff like this:

   diff -L k/<path> -L l/<path> -pu <old> <new>

   For added files, /dev/null is used for <old>.  For removed
   files, /dev/null is used for <new>

   The first part of the above command-line can be customized via
   the environment variable GIT_DIFF_CMD.  For example, if you
   do not want to show the extra level of leading path, you can
   say this:

   GIT_DIFF_CMD="diff -L'%s' -L'%s'" show-diff -p

   Caution:  Do not use more than two '%s' in GIT_DIFF_CMD.

   The diff formatting options can be customized via the
   environment variable GIT_DIFF_OPTS.  For example, if you
   prefer context diff:

   GIT_DIFF_OPTS=-c diff-cache -p $(cat .git/HEAD)


2. When the environment variable GIT_EXTERNAL_DIFF is set, the
   program named by it is called, instead of the diff invocation
   described above.

   For a path that is added, removed, or modified,
   GIT_EXTERNAL_DIFF is called with 7 parameters:

     path old-file old-hex old-mode new-file new-hex new-mode

   where
     <old|new>-file are files GIT_EXTERNAL_DIFF can use to read the
                    contents of <old|ne>,
     <old|new>-hex are the 40-hexdigit SHA1 hashes,
     <old|new>-mode are the octal representation of the file modes.

   The file parameters can point at the user's working file
   (e.g. new-file in show-diff), /dev/null (e.g. old-file when a
   new file is added), or a temporary file (e.g. old-file in the
   cache).  GIT_EXTERNAL_DIFF should not worry about
   unlinking the temporary file --- it is removed when
   GIT_EXTERNAL_DIFF exits.

   For a path that is unmerged, GIT_EXTERNAL_DIFF is called with
   1 parameter, path.

################################################################

Terminology: - see README for description
Each line contains terms used interchangeably

object database, .git directory
directory cache, index
id, sha1, sha1-id, sha1 hash
type, tag
blob, blob object
tree, tree object
commit, commit object
parent
root object
changeset


git Environment Variables
AUTHOR_NAME
AUTHOR_EMAIL
AUTHOR_DATE
COMMIT_AUTHOR_NAME
COMMIT_AUTHOR_EMAIL
GIT_DIFF_CMD
GIT_DIFF_OPTS
GIT_EXTERNAL_DIFF
GIT_INDEX_FILE
SHA1_FILE_DIRECTORY

Re: Quick command reference

[Junio C Hamano]

I suspect by now my endorsement would count at least a bit, so ...

DG> Please commit the version below (into a Documentation dir)
DG> and then all I have to do is send you patches to commit and
DG> you don't have to put too much effort into keeping it
DG> updated. It's 'only' docs - so although I may get it wrong,
DG> people like Junio will be sure to correct me.

Linus, I'm with David on this one.  I haven't reviewed his stuff
in this latest incarnation but I did review the draft a round
before and I felt it was accurate and ready for public (meaning
Porcelain layer writers and brave end users) consumption.

DG> I chose text to start since it could easily be read on the
DG> mailing list.  I'll gladly put it into some kind of markup
DG> later when the features start to stabilise.  For now people
DG> can wrap it in <pre> tags.

Linus, I'm with David on this one.  Text is Good.

Re: Quick command reference

[Junio C Hamano]

>>>>> "DG" == David Greaves <david@dgreaves.com> writes:

After I sent my endorsements, I noticed some nits so I pick them
here.  As you already know, you would also need to adjust to the
big git-* renaming.

DG> 	[Eventually may be replaced with <tree> if <tree> means
DG> 	<tree/commit> in all commands]

Probably not.  I think commit-tree should insist on its first
parameter being a tree not a commit for example, so I would drop
this comment.

Also tags are included in tree/commit class for some but
probably not all commands these days.  How about coming up with
a short-and-sweet name like <tree-id> and use it instead of
<tree/commit>?  You would need <commit-id> as well because tags
can be auto-dereferenced to commits by certain commands.

DG> <type>
DG> 	Indicates that an object type is required.
DG> 	Currently one of: blob/tree/commit

That's:

	Currently one of: blob/commit/tag/tree

DG> <file>
DG> 	Indicates a filename - often includes leading path
DG> <path>
DG> 	Indicates the path of a file (is this ever useful?)

I do not know what you wanted to distinguish by having separate
<file> and <path>.  There is only one thing.

We may want to mention that Core GIT expects the commands to run
from the directory that corresponds to the root level of the
tree structure GIT_INDEX_FILE describes, and the path/file
(whichever name you pick) are expected to be relative to that
directory.  No absolute paths, no ./relative paths with leading
dot-slash.

DG> ################################################################
DG> cat-file
DG> 	cat-file (-t | <type>) <object>
DG> ...
DG> <type>
DG> 	One of: blob/tree/commit
DG> ...
DG> Output
DG> If -t is specified, one of:
DG>         blob/tree/commit

Let's not list the type but refer the reader to the top part of
the document that lists the type.

DG> ################################################################
DG> checkout-cache
DG> ... Note that the file contents are
DG> restored - NOT the file permissions.
DG> ??? l 58 checkout-cache.c says restore executable bit.

So which is correct?

DG> ################################################################
DG> diff-tree-helper
DG> 	diff-tree-helper [-z]

Update:
	diff-tree-helper [-z] [-R]

Add:
        -R	generate the patch in reverse.

DG> ################################################################
DG> fsck-cache
DG> 	fsck-cache [[--unreachable] <commit>*]

--root?

DG> ################################################################
DG> show-diff
DG> 	show-diff [-p] [-q] [-s] [-z] [paths...]

After big git-* rename this became git-diff-files; just to keep
an eye on when you do the updates.

DG> ################################################################
DG> show-files

And this one is now git-ls-files.

DG> ################################################################
DG> unpack-file
DG> 	unpack-file <blob>

Add:

    Note that the temporary file is created with mkstemp(3) and it
    would have permission 0600 or 0666 depending on your glibc
    version.  Make sure to fix the permission if you use this in
    your script.

DG> ################################################################
DG> Generating patches

Please drop the following part.  GIT_DIFF_CMD is not supported
anymore:

DG>    The first part of the above command-line can be customized via
DG>    the environment variable GIT_DIFF_CMD...
DG>    ... 
DG>    Caution:  Do not use more than two '%s' in GIT_DIFF_CMD.

Drop it also from "git Environment Variables" section.

Re: Quick command reference

[H. Peter Anvin]

Brian O'Mahoney wrote:
> Thank you both for taking the time and trouble to do this, particularly
> with the name changes and new options; why don't you merge your efforts
> and produce a GIT-Mini-HOWTO BTW send it off as a patch again!

Even better... man page(s)!

	-hpa

Re: Quick command reference

[David Greaves]

H. Peter Anvin wrote:

> Brian O'Mahoney wrote:
>
>> Thank you both for taking the time and trouble to do this, particularly
>> with the name changes and new options; why don't you merge your efforts
>> and produce a GIT-Mini-HOWTO BTW send it off as a patch again!
>
>
> Even better... man page(s)!

Of course.

Eventually.

But I'd probably get limited reviewers if I posted nroff to the list...
(probably more than if I included html in my emails though)

:)

Nice to see there's a lot of support for and interest in getting the
docs though.
[Hmm, making statements like that with Linus on the cc - I could be in
politics ;) ]

David

Re: Quick command reference

[bert hubert]

On Sun, May 01, 2005 at 09:29:23AM -0700, Linus Torvalds wrote:
> (And no, by "standard format" I do _not_ mean xml or stuff like that. I 
> mean something that is actually easy to read ;)

I've recently been very happy with AsciiDoc
http://www.methods.co.nz/asciidoc/ - it's input is as easy to read as to
write.

>From this input:
http://ds9a.nl/splitpipe/splitpipe-0.3/doc/splitpipe.1.txt

It produces this lovely page (html, man, pdf, the works):
http://ds9a.nl/splitpipe/splitpipe-0.3/doc/splitpipe.1.html

And if you are really in a wild mood, you can have it make entire websites,
like http://ds9a.nl/splitpipe

When used properly it builds tables of contents, indexes, books and whatnot.

-- 
http://www.PowerDNS.com      Open source, database driven DNS Software 
http://netherlabs.nl              Open and Closed source services

Re: Quick command reference

[David Greaves]

bert hubert wrote:

>I've recently been very happy with AsciiDoc
>http://www.methods.co.nz/asciidoc/ - it's input is as easy to read as to
>write.
>  
>
sold

Re: Quick command reference

[Linus Torvalds]

On Sun, 1 May 2005, bert hubert wrote:
> 
> I've recently been very happy with AsciiDoc
> http://www.methods.co.nz/asciidoc/ - it's input is as easy to read as to
> write.

I have to agree. I don't much like most markup languages, but this one 
actually seems to truly _be_ readable even in its plain source format.

		Linus

Re: Quick command reference

[Randy.Dunlap]

On Sun, 1 May 2005 23:18:08 +0200 bert hubert wrote:

| On Sun, May 01, 2005 at 09:29:23AM -0700, Linus Torvalds wrote:
| > (And no, by "standard format" I do _not_ mean xml or stuff like that. I 
| > mean something that is actually easy to read ;)
| 
| I've recently been very happy with AsciiDoc
| http://www.methods.co.nz/asciidoc/ - it's input is as easy to read as to
| write.
| 
| >From this input:
| http://ds9a.nl/splitpipe/splitpipe-0.3/doc/splitpipe.1.txt
| 
| It produces this lovely page (html, man, pdf, the works):
| http://ds9a.nl/splitpipe/splitpipe-0.3/doc/splitpipe.1.html
| 
| And if you are really in a wild mood, you can have it make entire websites,
| like http://ds9a.nl/splitpipe
| 
| When used properly it builds tables of contents, indexes, books and whatnot.

AsciiDoc is already agreed upon, but here's another one that
I have used:  Markdown:
  http://daringfireball.net/projects/markdown/

---
~Randy

Quick command reference

[Junio C Hamano]

Linus, please pull from git-jc.git archive at:

    http://members.cox.net/junkio/git-jc.git/

(this time I have refs/heads/master there as well as HEAD; sorry
but no rsync).

I've added the Documentation directory as you suggested and
placed the copy of Quick reference David Greaves has been
working on.  I've minimally copy edited it to match the current
command names after the big git-* renaming, and also added
descriptions of commands and scripts that was missing back
then.  These three steps are recorded as separate commits (in
sequence, not Octopus).

The format is still plain text.  AsciiDoc can come in the next
round, but let's get the ball rolling by putting something in
there.

Please note that I do not intend to take the document over from
David.  I am just trying to help him get the result of his
effort into the mainline so that the document helps wider
audience, and to encourage (and remind) patch writers to keep it
up to date when modifying the Plumbing.

GIT blame (was Re: Quick command reference)

[Junio C Hamano]

>>>>> I == Junio C Hamano <junkio@cox.net> said:

JCH> Linus, please pull from git-jc.git archive at:
JCH>     http://members.cox.net/junkio/git-jc.git/

Since that message I have added a couple more commits there.
One of the things is a backport of -t (tag) flag to git-ls-files
from Cogito fork.

The reason I am writing this message is not because I am excited
about the backport [*1*], but because I find it quite cool the
way I found out which commit in Pasky's development line
introduced the change.  It demonstrates your previous "renames
does not matter when doing CVS blame" argument actually works.

Here is what I did:

  1. Go into git.pasky and look at ls-files.c, grab a couple of
     lines that look particular to Cogito version and store
     those lines in a file.  I used the following:

     $ cat >pattern <<\EOF
     static const char *tag_cached = "";
     static const char *tag_unmerged = "";
     static const char *tag_removed = "";
     static const char *tag_other = "";
     EOF

  2. Run the following command:

     $ jit-search-change HEAD pattern

What jit-search-change does is essentially what you described in
your "renames do not matter" argument.  It does git-rev-list to
list the commits from newer to older, runs git-diff-tree between
parent-commit pairs, with GIT_EXTERNAL_DIFF set to a script that
shows the diff between corresponding file in these two trees
only if the file from one tree has that pattern string and the
other tree's does not.  When it shows this diff, it also reports
the commit pair, and that's how you can find out which commit
introduced that change.

It currently shows useless hits when it sees merges from you to
Cogito, since those merges re-introduces the same change by
forward porting it over and over, which I am thinking about ways
to cull.  Maybe limiting the search only to parent-commit pair
that has only one parent would be good enough.  There are other
things to improve, but I am reasonably happy how it worked out.

[Footnote]

*1* The reason for the backport is because it is so small and
trivial change that does not affect the operation of the command
when the flag is not used.  I do not see a reason to force Pasky
to keep shipping the version modified for Cogito use.