[PATCH] add log.fulldiff config option

[PATCH] add log.fulldiff config option

[Jeff King]

This continues to default to 'off'.

Signed-off-by: Jeff King <peff@peff.net>
---
On Tue, Dec 19, 2006 at 05:17:17PM -0800, Junio C Hamano wrote:
> I typically do:
> 
>   git log --full-diff -p -SCOLLISION
> 
> The --full-diff option helps because it shows the diff for other
> files (that do not have different number of substring COLLISION
> in the pre and postimage) in the same commit as well.

I use --full-diff all the time, so this should save some typing. I can't
think of a time when I wouldn't want it on, but if there is, we probably
need a --no-full-diff.

Also, should this instead be diff.fulldiff?

Also also, I was going to submit a patch to document --full-diff,
but I had a few questions. Should it go in diff-options? That makes some
sense to me, but the parsing actually happens in setup_revisions.
Furthermore, it seems to do the same thing as --pickaxe-all. Should we
try to combine these?

 Documentation/config.txt |    6 ++++++
 builtin-log.c            |    6 ++++++
 2 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 22482d6..8be1fa6 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -248,6 +248,12 @@ i18n.commitEncoding::
 	browser (and possibly at other places in the future or in other
 	porcelains). See e.g. gitlink:git-mailinfo[1]. Defaults to 'utf-8'.
 
+log.fulldiff::
+	If true, log entries which have been selected through path-limiting
+	or pickaxe will show the diff for all files changed in that commit
+	instead of only the files matching the specified path or pickaxe
+	string.
+
 log.showroot::
 	If true, the initial commit will be shown as a big creation event.
 	This is equivalent to a diff against an empty tree.
diff --git a/builtin-log.c b/builtin-log.c
index 17014f7..57edd12 100644
--- a/builtin-log.c
+++ b/builtin-log.c
@@ -15,6 +15,7 @@
 #include <sys/time.h>
 
 static int default_show_root = 1;
+static int default_full_diff = 0;
 
 /* this is in builtin-diff.c */
 void add_head(struct rev_info *revs);
@@ -26,6 +27,7 @@ static void cmd_log_init(int argc, const char **argv, const char *prefix,
 	rev->commit_format = CMIT_FMT_DEFAULT;
 	rev->verbose_header = 1;
 	rev->show_root_diff = default_show_root;
+	rev->full_diff = default_full_diff;
 	argc = setup_revisions(argc, argv, rev, "HEAD");
 	if (rev->diffopt.pickaxe || rev->diffopt.filter)
 		rev->always_show_header = 0;
@@ -54,6 +56,10 @@ static int git_log_config(const char *var, const char *value)
 		default_show_root = git_config_bool(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "log.fulldiff")) {
+		default_full_diff = git_config_bool(var, value);
+		return 0;
+	}
 	return git_diff_ui_config(var, value);
 }
 
-- 

Re: [PATCH] add log.fulldiff config option

[Junio C Hamano]

Jeff King <peff@peff.net> writes:

> I use --full-diff all the time, so this should save some typing. I can't
> think of a time when I wouldn't want it on, but if there is, we probably
> need a --no-full-diff.

Absolutely.

> Also, should this instead be diff.fulldiff?

Probably not.

> Also also, I was going to submit a patch to document --full-diff,
> but I had a few questions. Should it go in diff-options? That makes some
> sense to me, but the parsing actually happens in setup_revisions.

Not at all.

> Furthermore, it seems to do the same thing as --pickaxe-all. Should we
> try to combine these?

No.

Try this with various combinations of with and without
the two flags.

    $ git log -1 -Sstate --full-diff --pickaxe-all b3d9899 -- git-fetch.sh

Your understanding needs to be clarified on how paths are
filtered, and how log family and diff interacts, and probably
these need to be better documented.

First, lets forget about 'log', but talk about diff (any of
diff-tree, diff-index --cached, diff-index, and diff-files).
They take paths as arguments.  The arguments limit the input
side of the diff.

    Side note: that is why "diff -C arch/x86_64" would not
    care about renames or copies from arch/i386 to
    arch/x86_64.  The diff machinery does not even see files
    under arch/i386 with that command line.

The pickaxe (-S) is defined at the 'diff' layer, and works as
the output filter from the 'diff' machinery.  It omits the
filepair (pair of preimage and postimage) whose both sides have
the same number of specified string in them ("pickaxe
criteria").

    $ git-diff-tree --name-status b3d9899

will show three paths, git-fetch.sh, git-ls-remote.sh, and
pkt-line.c.  But only git-fetch.sh matches the pickaxe criteria.
That's why:

    $ git-diff-tree -p -Sstate b3d9899

shows only git-fetch.sh and omits the other two paths.

The option --pickaxe-all changes this paths filtering to
all-or-none.  If any of the incoming paths matches the pickaxe
criteria, all changed paths, even the ones that do not match the
criteria, are included in the output.  Thus,

    $ git-diff-tree -p -Sstate --pickaxe-all b3d9899

gives three paths, although the other two paths do not change
the number of string "state".

With me so far?

Now, when you give paths to commands of the log family, they are
used to filter commits considered for the output by the revision
traversal machinery.  The revision machinery feeds only commits
whose tree is different from its parents at the specified paths
to the commands in the log family.  b3d9899 is eligible for
output in the first example because it changes "git-fetch.sh".

Then the commit is fed to the tree-diff machinery, with the same
paths limiter given to the log command.  If the diff machinery
says there is no interesting diff, the commit is not even
output.

    Side note: that is why

        $ git log -p -1 -Snosuchstring b3d9899 -- git-fetch.sh

    does not say anything.  Pickaxe says git-fetch.sh does not
    change "nosuchstring" and nothing comes out of the diff
    machinery.

What --full-diff does is to dissociate the paths limiter from
the diff machinery.  Before talking about pickaxe interaction,
let's try one without it.

Compare:

    $ git log -p -1             b3d9899 -- git-fetch.sh
    $ git log -p -1 --full-diff b3d9899 -- git-fetch.sh

In both, git-fetch.sh is first used by the revision traversal to
determine that b3d9899 is worth considering (the commit changes
that path).  Then the former uses the same paths limiter to
compute the diff for the commit.  Hence you will see only
git-fetch.sh.  The latter, however, does not use git-fetch.sh as
the paths limiter to generate diff because of --full-diff; it
feeds the full trees and that is why you can see three files.

Finally.

How do all of the above interact with the pickaxe?

    $ git log -p -1 -Sstate b3d9899 -- git-fetch.sh

Because git-fetch.sh is changed by b3d9899, revision traversal
makes the commit eligible.  It feeds that single path to diff
machinery and pickaxe says it changes "state".  Then it outputs
that path.

How about this one?

    $ git log -p -1 -Sstate --full-diff b3d9899 -- git-fetch.sh

git-fetch.sh makes b3d9899 eligible, --full-diff makes all three
paths touched by the commit (ignoring the paths you gave from
the command line) to be fed to the diff machinery, and pickaxe
picks git-fetch.sh because that is the only one that changes
"state".  For the same reason, you would see git-fetch.sh out of
this one:

    $ git log -p -1 -Sstate --full-diff b3d9899 -- pkt-line.c

Truly finally.

If you add --pickaxe-all to the last one:

    $ git log -p -1 -Sstate --pickaxe-all --full-diff b3d9899 -- pkt-line.c

pkt-line.c makes b3d9899 eligible, --full-diff feeds three
changed paths to diff machinery, pickaxe notices that one of
them (git-fetch.sh which is different from what you gave from
the command line) changes "state", --pickaxe-all causes all
three incoming paths to be output.

[PATCH] revision: add --no-full-diff command line option

[Jeff King]

Signed-off-by: Jeff King <peff@peff.net>
---
On Wed, Dec 20, 2006 at 12:14:14AM -0800, Junio C Hamano wrote:

> > I use --full-diff all the time, so this should save some typing. I can't
> > think of a time when I wouldn't want it on, but if there is, we probably
> > need a --no-full-diff.
> 
> Absolutely.

I took this to mean "absolutely we need --no-full-diff." :)

I note that --full-diff sets rev->diff = 1. The log.fulldiff config
option does not, and nor does --no-full-diff unset it. However, I'm not
sure it makes sense to set it. Doing "git-log --full-diff" outputs an
extra line (separating the diff from the commit log) but since we
haven't told it any type of diff to output, the diff is blank. And if we
had told it a type, then that would have turned on rev->diff. So I don't
see a point in setting it.

 revision.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/revision.c b/revision.c
index 56819f8..ac4dbf2 100644
--- a/revision.c
+++ b/revision.c
@@ -955,6 +955,10 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, const ch
 				revs->full_diff = 1;
 				continue;
 			}
+			if (!strcmp(arg, "--no-full-diff")) {
+				revs->full_diff = 0;
+				continue;
+			}
 			if (!strcmp(arg, "--full-history")) {
 				revs->simplify_history = 0;
 				continue;
-- 
1.4.4.2.gee7ba-dirty

Re: [PATCH] revision: add --no-full-diff command line option

[Junio C Hamano]

Jeff King <peff@peff.net> writes:

> Signed-off-by: Jeff King <peff@peff.net>
> ---
> On Wed, Dec 20, 2006 at 12:14:14AM -0800, Junio C Hamano wrote:
>
>> > I use --full-diff all the time, so this should save some typing. I can't
>> > think of a time when I wouldn't want it on, but if there is, we probably
>> > need a --no-full-diff.
>> 
>> Absolutely.
>
> I took this to mean "absolutely we need --no-full-diff." :)

Modulo s/\.$/, if we were to do log.fulldiff/, yes.

> I note that --full-diff sets rev->diff = 1. The log.fulldiff config
> option does not, and nor does --no-full-diff unset it. However, I'm not
> sure it makes sense to set it. Doing "git-log --full-diff" outputs an
> extra line (separating the diff from the commit log) but since we
> haven't told it any type of diff to output, the diff is blank. And if we
> had told it a type, then that would have turned on rev->diff. So I don't
> see a point in setting it.

I need to think about this one.

Re: [PATCH] add log.fulldiff config option

[Jeff King]

On Wed, Dec 20, 2006 at 12:14:14AM -0800, Junio C Hamano wrote:

> > Also, should this instead be diff.fulldiff?
> 
> Probably not.

Based on your explanation, I think that makes sense.

> > Also also, I was going to submit a patch to document --full-diff,
> > but I had a few questions. Should it go in diff-options? That makes some
> > sense to me, but the parsing actually happens in setup_revisions.
> 
> Not at all.

Then where should it go? whatchanged and log have a great deal of
overlap in terms of parsing, but they don't seem to share any
documentation (or note the fact that git-whatchanged is basically just
git-log -p).

> > Furthermore, it seems to do the same thing as --pickaxe-all. Should we
> > try to combine these?
> 
> No.

Thanks for the thorough explanation. I think this makes my config option
description a little bit off, then, since it doesn't actually show all
of the changed files for a commit in the case of pickaxe.

What has me confused, then, is that you said this:

> I typically do:
> 
>         git log --full-diff -p -SCOLLISION
> 
> The --full-diff option helps because it shows the diff for other
> files (that do not have different number of substring COLLISION
> in the pre and postimage) in the same commit as well.

But that isn't the case, AFAIK (e.g., the command line you mention shows
only changes to sha1_file.c in commit aac17941, but cache.h was also
changed). Did you mean --pickaxe-all?

> Your understanding needs to be clarified on how paths are
> filtered, and how log family and diff interacts, and probably
> these need to be better documented.

To be honest, I'm not sure when one would really _want_ the flexibility
this provides. It might be more intuitive to git-{log,whatchanged} users
to have a single option (config and command line) to set --full-diff and
--pickaxe-all together. At the very least, I think I now want a
diff.pickaxeall config option.

Re: [PATCH] add log.fulldiff config option

[Junio C Hamano]

Junio C Hamano <junkio@cox.net> writes:

> Your understanding needs to be clarified on how paths are
> filtered, and how log family and diff interacts, and probably
> these need to be better documented.

Having said that, I realized that I was making the same mistake
that our existing documentation was criticized for.

Let me first digress to address the documentation criticism.
The description on plumbing were (and still are) far more
thorough than porcelain-ish, and the conjecture by the person
who criticized them was because developers were keen documenting
the real work (plumbing) soon after they finished coding than
the frill (porcelain-ish).

I think the real reason for this is somewhat different.  At
least to me, git.git was about the plumbing, and I did not want
to be in the Porcelain business at all [*1*].  Instead, I wanted
to encourage healthy competition among Porcelains.  What was
shipped with git.git was meant to be "barely usable examples".
But this vision has not materialized fully yet, fortunately
because we did not end up splitting the userbase too early on.
But this was unfortunate for two reasons.  One of them is that
different Porcelains would have brought completely different
ways of thinking and workflows into the picture.

Because git.git was primarily about the plumbing, the main focus
of the interface the plumbing offers was not about integration
and uniformity but modularity.  Designing them as independent
building blocks as much as practical, and describing them fully,
were part of completing the plumbing.  And the "barely usable
examples" started their lives as a set of trivial pipelines,
whose meaning was quite obvious and straightforward when you
understand the plumbing parts used in them.  It also had UI
warts.  "barely usable examples" cheated their command line
parsing, and the flags used by the plumbing showed through its
thin veneer to the UI used by the end users.

But that was a long time ago.  Now we are in the v1.5.0 process,
whose theme is "usability and teachability".

Now, viewing in that light, what I described in the previous
message may have been a precise description of how things happen
to work currently, but it was not about the reason how and why
they were designed to be (because there was little design at the
UI level).  We should instead (or at least "in addition") be
talking more about how things ought to be.

I described why --full-diff and --pickaxe-all are different
options, you can give 4 combinations of them, and how the
combinations work differently and why.  That does not justify
that all of these four combinations make sense.  In fact, I do
not think they do.

When pickaxe is used and --full-diff is given to 'log', I think
it does not make any sense not to use --pickaxe-all.  So, I
think at the level of log family commands, unifying these two
flags make a lot of sense (although I earlier said "no").

Although --diff-filter does not have a corresponding option that
makes it behave all-or-none (i.e. an equivalent to --pickaxe-all),
it is conceivable that you might want to say:

    $ git log --diff-filter=A --full-diff --diff-filter-all

to view commits that add new files with full diffs (not just
added paths).  If we were to add that, I think it makes sense to
internally have a flag separate from pickaxe-all to express it
but when 'log' uses --full-diff, it does not make any sense not
to enable it.  In other words,

    $ git log -M --diff-filter=R -Sstring --full-diff

should internally enable pickaxe-all and diff-filter-all and
show all of diff that has renames in the paths that change
"string" [*2*].


[Footnote]

*1* I once wanted to do a Porcelain of my own, after finding it
distasteful that Cogito tried to hide the index back when it did
not even use the index properly for merges.  But things have
been improved quite a lot in Cogito land and I do not have
anything against it anymore.  And as you all know, I like StGIT
very much.

*2* This is actually in line with what we did in 582af688.  As a
member of 'log' family, 'git log' were originally meant to show
commit messages for all commits that revision traversal gave it,
regardless of the diff output (and without the diffcore
transformation, when revision traversal said a commit is
interesting, the commit always has some diff or a merge).  When
used in conjunction with --pickaxe and --diff-filter, however,
this layering made the command much less useful.  We fixed the
problem by violating the layering and made the log command aware
of the underlying diff machinery's output filter.  I think the
same would apply to the issue we are currently discussing.