From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LxzfU-0006ZC-DJ for qemu-devel@nongnu.org; Sun, 26 Apr 2009 04:24:56 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LxzfP-0006QZ-8R for qemu-devel@nongnu.org; Sun, 26 Apr 2009 04:24:55 -0400 Received: from [199.232.76.173] (port=40970 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LxzfP-0006QC-1q for qemu-devel@nongnu.org; Sun, 26 Apr 2009 04:24:51 -0400 Received: from mx20.gnu.org ([199.232.41.8]:62863) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1LxzfO-0006ka-86 for qemu-devel@nongnu.org; Sun, 26 Apr 2009 04:24:50 -0400 Received: from ftp.linux-mips.org ([213.58.128.207]) by mx20.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1LxzfJ-0006hk-GG for qemu-devel@nongnu.org; Sun, 26 Apr 2009 04:24:46 -0400 Received: from localhost.localdomain ([127.0.0.1]:35772 "EHLO h5.dl5rb.org.uk" rhost-flags-OK-OK-OK-FAIL) by ftp.linux-mips.org with ESMTP id S20024087AbZDZIYj convert rfc822-to-quoted-printable (ORCPT ); Sun, 26 Apr 2009 09:24:39 +0100 Resent-Message-ID: <20090426082432.GB18799@linux-mips.org> Resent-To: imp@bsdimp.com, qemu-devel@nongnu.org, mle+tools@mega-nerd.com Date: Sun, 26 Apr 2009 10:15:16 +0200 From: Ralf Baechle Subject: Re: [Qemu-devel] Switch to GIT. Why? Message-ID: <20090426081516.GA18300@linux-mips.org> References: <20090426155257.7c6dac29.mle+tools@mega-nerd.com> <20090426.011320.1172763085.imp@bsdimp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: QUOTED-PRINTABLE In-Reply-To: <20090426.011320.1172763085.imp@bsdimp.com> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "M. Warner Losh" Cc: mle+tools@mega-nerd.com, qemu-devel@nongnu.org On Sun, Apr 26, 2009 at 01:13:20AM -0600, M. Warner Losh wrote: > : > Is it possible to set it up so that GIT has an SVN back-end? > :=20 > : Not that I know of. >=20 > I thought I saw an email go by that it was already setup... I assume you're talking about the git-svn command? Just like git's CVS interoperability it's a nice tool but in the end it should only be used to make the pains of migration more bareable. I don't think git-cvsserver for example is a great thing in the longer ru= n nor does git-svn seem to be. Ralf GIT-SVN(1) Git Manual GIT-SVN(1) NAME git-svn - Bidirectional operation between a single Subversion br= anch and git SYNOPSIS git svn [options] [arguments] DESCRIPTION git-svn is a simple conduit for changesets between Subversion an= d git. It provides a bidirectional flow of changes between a Subversion= and a git repository. git-svn can track a single Subversion branch simply by using a U= RL to the branch, follow branches laid out in the Subversion recommend= ed method (trunk, branches, tags directories) with the --stdlayout = option, or follow branches in any layout with the -T/-t/-b options (see = options to init below, and also the clone command). Once tracking a Subversion branch (with any of the above methods= ), the git repository can be updated from Subversion by the fetch comma= nd and Subversion updated from git by the dcommit command. COMMANDS init Initializes an empty git repository with additional metadata directories for git-svn. The Subversion URL may be specified as a command-line argument, or as full URL arguments to -T/-t/-b. Optionally, the target directory to operate on can be specified as a second argument. Normally this command initializes the current directory. -T, --trunk=3D, -t, --tags=3D, -b, --branches=3D, -s, --stdlayout These are optional command-line options for init. Each of these flags can point to a relative repository path (--tags=3Dproject/tags=C2=B4) or a full url (--tags=3Dhttps://foo.org/project/tags). The option --stdlayout is a shorthand way of setting trunk,tags,branches as the relative paths, which is the Subversion default. If any of the other options are given as well, they take precedence. --no-metadata Set the noMetadata option in the [svn-remote] config. --use-svm-props Set the useSvmProps option in the [svn-remote] config. --use-svnsync-props Set the useSvnsyncProps option in the [svn-remote] config. --rewrite-root=3D Set the rewriteRoot option in the [svn-remote] config. --use-log-author When retrieving svn commits into git (as part of fetch, rebase, or dcommit operations), look for the first From: or Signed-off-by: line in the log message and use that as the author string. --add-author-from When committing to svn from git (as part of commit or dcommit operations), if the existing log message doesn=C2=B4t already h= ave a From: or Signed-off-by: line, append a From: line based on the git commit=C2=B4s author string. If you use this, then --use-log-author will retrieve a valid author string for all commits. --username=3D For transports that SVN handles authentication for (http, https, and plain svn), specify the username. For other transports (eg svn+ssh://), you must include the username in the URL, eg svn+ssh://foo@svn.bar.com/project --prefix=3D This allows one to specify a prefix which is prepended to the names of remotes if trunk/branches/tags are specified. The prefix does not automatically include a trailing slash, so be sure you include one in the argument if that is what you want. If --branches/-b is specified, the prefix must include a trailing slash. Setting a prefix is useful if you wish to track multiple projects that share a common repository. fetch Fetch unfetched revisions from the Subversion remote we are tracking. The name of the [svn-remote "..."] section in the .git/config file may be specified as an optional command-line argument. clone Runs init and fetch. It will automatically create a directory based on the basename of the URL passed to it; or if a second argument is passed; it will create a directory and work within that. It accepts all arguments that the init and fetch commands accept; with the exception of --fetch-all. After a repository is cloned, the fetch command will be able to update revisions without affecting the working tree; and the rebase command will be able to update the working tree with the latest changes. rebase This fetches revisions from the SVN parent of the current HEAD and rebases the current (uncommitted to SVN) work against it. This works similarly to svn update or git-pull except that it preserves linear history with git-rebase instead of git-merge for ease of dcommitting with git-svn. This accepts all options that git-svn fetch and git-rebase accept. However, --fetch-all only fetches from the current [svn-remote], and not all [svn-remote] definitions. Like git-rebase; this requires that the working tree be clean and have no uncommitted changes. -l, --local Do not fetch remotely; only run git-rebase against the last fetched commit from the upstream SVN. dcommit Commit each diff from a specified head directly to the SVN repository, and then rebase or reset (depending on whether or not there is a diff between SVN and head). This will create a revision in SVN for each commit in git. It is recommended that you run git-svn fetch and rebase (not pull or merge) your commits against the latest changes in the SVN repository. An optional command-line argument may be specified as an alternative to HEAD. This is advantageous over set-tree (below) because it produces cleaner, more linear history. --no-rebase After committing, do not rebase or reset. --commit-url Commit to this SVN URL (the full path). This is intended to allow existing git-svn repositories created with one transport method (e.g. svn:// or http:// for anonymous read) to be reused if a user is later given access to an alternate transport method (e.g. svn+ssh:// or https://) for commit. Using this option for any other purpose (don=C2=B4t ask) is very strongly discouraged. log This should make it easy to look up svn log messages when svn users refer to -r/--revision numbers. The following features from =E2=80=98svn log=C2=B4 are supported: --revision=3D[:] is supported, non-numeric args are not: HEAD, NEXT, BASE, PREV, etc ... -v/--verbose it=C2=B4s not completely compatible with the --verbose output i= n svn log, but reasonably close. --limit=3D is NOT the same as --max-count, doesn=C2=B4t count merged/exclu= ded commits --incremental supported New features: --show-commit shows the git commit sha1, as well --oneline our version of --pretty=3Doneline Note SVN itself only stores times in UTC and nothing else. The regular svn client converts the UTC time to the local time (or based on the TZ=3D environment). This command has the same behaviour. Any other arguments are passed directly to git-log blame Show what revision and author last modified each line of a file. The output of this mode is format-compatible with the output of =E2=80=98svn blame=C2=B4 by default. Like the SVN blame command, lo= cal uncommitted changes in the working copy are ignored; the version of the file in the HEAD revision is annotated. Unknown arguments are passed directly to git-blame. --git-format Produce output in the same format as git-blame, but with SVN revision numbers instead of git commit hashes. In this mode, changes that haven=C2=B4t been committed to SVN (including loca= l working-copy edits) are shown as revision 0. find-rev When given an SVN revision number of the form rN, returns the corresponding git commit hash (this can optionally be followed by a tree-ish to specify which branch should be searched). When given a tree-ish, returns the corresponding SVN revision number. set-tree You should consider using dcommit instead of this command. Commit specified commit or tree objects to SVN. This relies on your imported fetch data being up-to-date. This makes absolutely no attempts to do patching when committing to SVN, it simply overwrites files with those specified in the tree or commit. All merging is assumed to have taken place independently of git-svn functions. create-ignore Recursively finds the svn:ignore property on directories and creates matching .gitignore files. The resulting files are staged to be committed, but are not committed. Use -r/--revision to refer to a specific revision. show-ignore Recursively finds and lists the svn:ignore property on directories. The output is suitable for appending to the $GIT_DIR/info/exclude file. commit-diff Commits the diff of two tree-ish arguments from the command-line. This command does not rely on being inside an git-svn init-ed repository. This command takes three arguments, (a) the original tree to diff against, (b) the new tree result, (c) the URL of the target Subversion repository. The final argument (URL) may be omitted if you are working from a git-svn-aware repository (that has been init-ed with git-svn). The -r option is required for this. info Shows information about a file or directory similar to what =E2=80=98= svn info=C2=B4 provides. Does not currently support a -r/--revision argument. Use the --url option to output only the value of the URL: field. proplist Lists the properties stored in the Subversion repository about a given file or directory. Use -r/--revision to refer to a specific Subversion revision. propget Gets the Subversion property given as the first argument, for a file. A specific revision can be specified with -r/--revision. show-externals Shows the Subversion externals. Use -r/--revision to specify a specific revision. OPTIONS --shared[=3D{false|true|umask|group|all|world|everybody}], --template=3D Only used with the init command. These are passed directly to git-init. -r , --revision Used with the fetch command. This allows revision ranges for partial/cauterized history to be supported. $NUMBER, $NUMBER1:$NUMBER2 (numeric ranges), $NUMBER:HEAD, and BASE:$NUMBER are all supported. This can allow you to make partial mirrors when running fetch; but is generally not recommended because history will be skipped and lost. -, --stdin Only used with the set-tree command. Read a list of commits from stdin and commit them in reverse order. Only the leading sha1 is read from each line, so git-rev-list --pretty=3Doneline output can be used. --rmdir Only used with the dcommit, set-tree and commit-diff commands. Remove directories from the SVN tree if there are no files left behind. SVN can version empty directories, and they are not removed by default if there are no files left in them. git cannot version empty directories. Enabling this flag will make the commit to SVN act like git. config key: svn.rmdir -e, --edit Only used with the dcommit, set-tree and commit-diff commands. Edit the commit message before committing to SVN. This is off by default for objects that are commits, and forced on when committing tree objects. config key: svn.edit -l, --find-copies-harder Only used with the dcommit, set-tree and commit-diff commands. They are both passed directly to git-diff-tree; see git-diff- tree(1) for more information. config key: svn.l config key: svn.findcopiesharder -A, --authors-file=3D Syntax is compatible with the file used by git-cvsimport: .ft C loginname =3D Joe User .ft If this option is specified and git-svn encounters an SVN committer name that does not exist in the authors-file, git-svn will abort operation. The user will then have to add the appropriate entry. Re-running the previous git-svn command after the authors-file is modified should continue operation. config key: svn.authorsfile -q, --quiet Make git-svn less verbose. --repack[=3D], --repack-flags=3D These should help keep disk usage sane for large fetches with many revisions. --repack takes an optional argument for the number of revisions to fetch before repacking. This defaults to repacking every 1000 commits fetched if no argument is specified. --repack-flags are passed directly to git-repack. config key: svn.repack config key: svn.repackflags -m, --merge, -s, --strategy=3D These are only used with the dcommit and rebase commands. Passed directly to git-rebase when using dcommit if a git-reset cannot be used (see dcommit). -n, --dry-run This can be used with the dcommit and rebase commands. For dcommit, print out the series of git arguments that would show which diffs would be committed to SVN. For rebase, display the local branch associated with the upstream svn repository associated with the current branch and the URL of svn repository that will be fetched from. ADVANCED OPTIONS -i, --id This sets GIT_SVN_ID (instead of using the environment). This allows the user to override the default refname to fetch from when tracking a single URL. The log and dcommit commands no longer require this switch as an argument. -R, --svn-remote Specify the [svn-remote ""] section to use, this allows SVN multiple repositories to be tracked. Default: "svn" --follow-parent This is especially helpful when we=C2=B4re tracking a directory tha= t has been moved around within the repository, or if we started tracking a branch and never tracked the trunk it was descended from. This feature is enabled by default, use --no-follow-parent to disable it. config key: svn.followparent CONFIG FILE-ONLY OPTIONS svn.noMetadata, svn-remote..noMetadata This gets rid of the git-svn-id: lines at the end of every commit. If you lose your .git/svn/git-svn/.rev_db file, git-svn will not be able to rebuild it and you won=C2=B4t be able to fetch again, eithe= r. This is fine for one-shot imports. The git-svn log command will not work on repositories using this, either. Using this conflicts with the useSvmProps option for (hopefully) obvious reasons. svn.useSvmProps, svn-remote..useSvmProps This allows git-svn to re-map repository URLs and UUIDs from mirrors created using SVN::Mirror (or svk) for metadata. If an SVN revision has a property, "svm:headrev", it is likely that the revision was created by SVN::Mirror (also used by SVK). The property contains a repository UUID and a revision. We want to make it look like we are mirroring the original URL, so introduce a helper function that returns the original identity URL and UUID, and use it when generating metadata in commit messages. svn.useSvnsyncProps, svn-remote..useSvnsyncprops Similar to the useSvmProps option; this is for users of the svnsync(1) command distributed with SVN 1.4.x and later. svn-remote..rewriteRoot This allows users to create repositories from alternate URLs. For example, an administrator could run git-svn on the server locally (accessing via file://) but wish to distribute the repository with a public http:// or svn:// URL in the metadata so users of it will see the public URL. Since the noMetadata, rewriteRoot, useSvnsyncProps and useSvmPro= ps options all affect the metadata generated and used by git-svn; t= hey must be set in the configuration file before any history is impo= rted and these settings should never be changed once they are set. Additionally, only one of these four options can be used per-svn= -remote section because they affect the git-svn-id: metadata line. BASIC EXAMPLES Tracking and contributing to the trunk of a Subversion-managed p= roject: .ft C # Clone a repo (like git clone): git svn clone http://svn.example.com/project/trunk # Enter the newly cloned directory: cd trunk # You should be on master branch, double-check with git-branch git branch # Do some work and commit locally to git: git commit ... # Something is committed to SVN, rebase your local changes against = the # latest changes in SVN: git svn rebase # Now commit your changes (that were committed previously using git= ) to SVN, # as well as automatically updating your working HEAD: git svn dcommit # Append svn:ignore settings to the default git exclude file: git svn show-ignore >> .git/info/exclude .ft Tracking and contributing to an entire Subversion-managed projec= t (complete with a trunk, tags and branches): .ft C # Clone a repo (like git clone): git svn clone http://svn.example.com/project -T trunk -b branches = -t tags # View all branches and tags you have cloned: git branch -r # Reset your master to trunk (or any other branch, replacing =C2=B4= trunk=C2=B4 # with the appropriate name): git reset --hard remotes/trunk # You may only dcommit to one branch/tag/trunk at a time. The usag= e # of dcommit/rebase/show-ignore should be the same as above. .ft The initial git-svn clone can be quite time-consuming (especiall= y for large Subversion repositories). If multiple people (or one perso= n with multiple machines) want to use git-svn to interact with the same Subversion repository, you can do the initial git-svn clone to a repository on a server and have each person clone that repositor= y with git-clone: .ft C # Do the initial import on a server ssh server "cd /pub && git svn clone http://svn.example.com/projec= t # Clone locally - make sure the refs/remotes/ space matches the ser= ver mkdir project cd project git init git remote add origin server:/pub/project git config --add remote.origin.fetch =C2=B4+refs/remotes/*:refs/re= motes/*=C2=B4 git fetch # Create a local branch from one of the branches just fetched git checkout -b master FETCH_HEAD # Initialize git-svn locally (be sure to use the same URL and -T/-b= /-t options as were used on server) git svn init http://svn.example.com/project # Pull the latest changes from Subversion git svn rebase .ft REBASE VS. PULL/MERGE Originally, git-svn recommended that the remotes/git-svn branch = be pulled or merged from. This is because the author favored git sv= n set-tree B to commit a single head rather than the git svn set-t= ree A..B notation to commit multiple commits. If you use git svn set-tree A..B to commit several diffs and you= do not have the latest remotes/git-svn merged into my-branch, you shoul= d use git svn rebase to update your work branch instead of git pull or= git merge. pull/=E2=80=98merge=C2=B4 can cause non-linear history to= be flattened when committing into SVN, which can lead to merge commits reversing p= revious commits in SVN. DESIGN PHILOSOPHY Merge tracking in Subversion is lacking and doing branched devel= opment with Subversion can be cumbersome as a result. While git-svn can= track copy history (including branches and tags) for repositories adop= ting a standard layout, it cannot yet represent merge history that happ= ened inside git back upstream to SVN users. Therefore it is advised t= hat users keep history as linear as possible inside git to ease compatibility with SVN (see the CAVEATS section below). CAVEATS For the sake of simplicity and interoperating with a less-capabl= e system (SVN), it is recommended that all git-svn users clone, fe= tch and dcommit directly from the SVN server, and avoid all git-clone/pull/merge/push operations between git repositories an= d branches. The recommended method of exchanging code between git branches and users is git-format-patch and git-am, or just =C2=B4= dcommit=C2=B4ing to the SVN repository. Running git-merge or git-pull is NOT recommended on a branch you= plan to dcommit from. Subversion does not represent merges in any rea= sonable or useful fashion; so users using Subversion cannot see any merg= es you=C2=B4ve made. Furthermore, if you merge or pull from a git b= ranch that is a mirror of an SVN branch, dcommit may commit to the wrong br= anch. git-clone does not clone branches under the refs/remotes/ hierar= chy or any git-svn metadata, or config. So repositories created and man= aged with using git-svn should use rsync for cloning, if cloning is t= o be done at all. Since dcommit uses rebase internally, any git branches you git-p= ush to before dcommit on will require forcing an overwrite of the exist= ing ref on the remote repository. This is generally considered bad pract= ice, see the git-push(1) documentation for details. Do not use the --amend option of git-commit(1) on a change you=C2= =B4ve already dcommitted. It is considered bad practice to --amend com= mits you=C2=B4ve already pushed to a remote repository for other user= s, and dcommit with SVN is analogous to that. BUGS We ignore all SVN properties except svn:executable. Any unhandle= d properties are logged to $GIT_DIR/svn//unhandled.log Renamed and copied directories are not detected by git and hence= not tracked when committing to SVN. I do not plan on adding support = for this as it=C2=B4s quite difficult and time-consuming to get work= ing for all the possible corner cases (git doesn=C2=B4t do it, either). Comm= itting renamed and copied files are fully supported if they=C2=B4re sim= ilar enough for git to detect them. CONFIGURATION git-svn stores [svn-remote] configuration information in the rep= ository .git/config file. It is similar the core git [remote] sections e= xcept fetch keys do not accept glob arguments; but they are instead ha= ndled by the branches and tags keys. Since some SVN repositories are o= ddly configured with multiple projects glob expansions such those lis= ted below are allowed: .ft C [svn-remote "project-a"] url =3D http://server.org/svn branches =3D branches/*/project-a:refs/remotes/project-a/branches/= * tags =3D tags/*/project-a:refs/remotes/project-a/tags/* trunk =3D trunk/project-a:refs/remotes/project-a/trunk .ft Keep in mind that the (asterisk) wildcard of the local ref (rig= ht of the :) *must be the farthest right path component; however the r= emote wildcard may be anywhere as long as it=C2=B4s own independent pa= th component (surrounded by / or EOL). This type of configuration is not automatically created by init and should be manually entered wit= h a text-editor or using git-config. SEE ALSO git-rebase(1) AUTHOR Written by Eric Wong . DOCUMENTATION Written by Eric Wong . Git 1.6.0.6 03/02/2009 GIT-SVN(1)