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GIT-FILTER-BRANCH(1) | Git Manual | GIT-FILTER-BRANCH(1) |
NAME¶
git-filter-branch - Rewrite branchesSYNOPSIS¶
git filter-branch [--env-filter <command>] [--tree-filter <command>] [--index-filter <command>] [--parent-filter <command>] [--msg-filter <command>] [--commit-filter <command>] [--tag-name-filter <command>] [--subdirectory-filter <directory>] [--prune-empty] [--original <namespace>] [-d <directory>] [-f | --force] [--] [<rev-list options>...]
DESCRIPTION¶
Lets you rewrite Git revision history by rewriting the branches mentioned in the <rev-list options>, applying custom filters on each revision. Those filters can modify each tree (e.g. removing a file or running a perl rewrite on all files) or information about each commit. Otherwise, all information (including original commit times or merge information) will be preserved. The command will only rewrite the positive refs mentioned in the command line (e.g. if you pass a..b, only b will be rewritten). If you specify no filters, the commits will be recommitted without any changes, which would normally have no effect. Nevertheless, this may be useful in the future for compensating for some Git bugs or such, therefore such a usage is permitted. NOTE: This command honors .git/info/grafts file and refs in the refs/replace/ namespace. If you have any grafts or replacement refs defined, running this command will make them permanent. WARNING! The rewritten history will have different object names for all the objects and will not converge with the original branch. You will not be able to easily push and distribute the rewritten branch on top of the original branch. Please do not use this command if you do not know the full implications, and avoid using it anyway, if a simple single commit would suffice to fix your problem. (See the "RECOVERING FROM UPSTREAM REBASE" section in git-rebase(1) for further information about rewriting published history.) Always verify that the rewritten version is correct: The original refs, if different from the rewritten ones, will be stored in the namespace refs/original/. Note that since this operation is very I/O expensive, it might be a good idea to redirect the temporary directory off-disk with the -d option, e.g. on tmpfs. Reportedly the speedup is very noticeable.Filters¶
The filters are applied in the order as listed below. The <command> argument is always evaluated in the shell context using the eval command (with the notable exception of the commit filter, for technical reasons). Prior to that, the $GIT_COMMIT environment variable will be set to contain the id of the commit being rewritten. Also, GIT_AUTHOR_NAME, GIT_AUTHOR_EMAIL, GIT_AUTHOR_DATE, GIT_COMMITTER_NAME, GIT_COMMITTER_EMAIL, and GIT_COMMITTER_DATE are taken from the current commit and exported to the environment, in order to affect the author and committer identities of the replacement commit created by git-commit-tree(1) after the filters have run. If any evaluation of <command> returns a non-zero exit status, the whole operation will be aborted. A map function is available that takes an "original sha1 id" argument and outputs a "rewritten sha1 id" if the commit has been already rewritten, and "original sha1 id" otherwise; the map function can return several ids on separate lines if your commit filter emitted multiple commits.OPTIONS¶
--env-filter <command>This filter may be used if you only need to modify the
environment in which the commit will be performed. Specifically, you might
want to rewrite the author/committer name/email/time environment variables
(see git-commit-tree(1) for details). Do not forget to re-export the
variables.
--tree-filter <command>
This is the filter for rewriting the tree and its
contents. The argument is evaluated in shell with the working directory set to
the root of the checked out tree. The new tree is then used as-is (new files
are auto-added, disappeared files are auto-removed - neither .gitignore files
nor any other ignore rules HAVE ANY EFFECT!).
--index-filter <command>
This is the filter for rewriting the index. It is similar
to the tree filter but does not check out the tree, which makes it much
faster. Frequently used with git rm --cached --ignore-unmatch ..., see
EXAMPLES below. For hairy cases, see git-update-index(1).
--parent-filter <command>
This is the filter for rewriting the commit’s
parent list. It will receive the parent string on stdin and shall output the
new parent string on stdout. The parent string is in the format described in
git-commit-tree(1): empty for the initial commit, "-p parent"
for a normal commit and "-p parent1 -p parent2 -p parent3 ..." for a
merge commit.
--msg-filter <command>
This is the filter for rewriting the commit messages. The
argument is evaluated in the shell with the original commit message on
standard input; its standard output is used as the new commit message.
--commit-filter <command>
This is the filter for performing the commit. If this
filter is specified, it will be called instead of the git commit-tree
command, with arguments of the form "<TREE_ID> [(-p
<PARENT_COMMIT_ID>)...]" and the log message on stdin. The commit
id is expected on stdout.
As a special extension, the commit filter may emit multiple commit ids; in that
case, the rewritten children of the original commit will have all of them as
parents.
You can use the map convenience function in this filter, and other
convenience functions, too. For example, calling skip_commit
"$@" will leave out the current commit (but not its changes! If
you want that, use git rebase instead).
You can also use the git_commit_non_empty_tree "$@" instead of git
commit-tree "$@" if you don’t wish to keep commits with a
single parent and that makes no change to the tree.
--tag-name-filter <command>
This is the filter for rewriting tag names. When passed,
it will be called for every tag ref that points to a rewritten object (or to a
tag object which points to a rewritten object). The original tag name is
passed via standard input, and the new tag name is expected on standard
output.
The original tags are not deleted, but can be overwritten; use
"--tag-name-filter cat" to simply update the tags. In this case, be
very careful and make sure you have the old tags backed up in case the
conversion has run afoul.
Nearly proper rewriting of tag objects is supported. If the tag has a message
attached, a new tag object will be created with the same message, author, and
timestamp. If the tag has a signature attached, the signature will be
stripped. It is by definition impossible to preserve signatures. The reason
this is "nearly" proper, is because ideally if the tag did not
change (points to the same object, has the same name, etc.) it should retain
any signature. That is not the case, signatures will always be removed, buyer
beware. There is also no support for changing the author or timestamp (or the
tag message for that matter). Tags which point to other tags will be rewritten
to point to the underlying commit.
--subdirectory-filter <directory>
Only look at the history which touches the given
subdirectory. The result will contain that directory (and only that) as its
project root. Implies the section called “Remap to
ancestor”.
--prune-empty
Some kind of filters will generate empty commits, that
left the tree untouched. This switch allow git-filter-branch to ignore such
commits. Though, this switch only applies for commits that have one and only
one parent, it will hence keep merges points. Also, this option is not
compatible with the use of --commit-filter. Though you just need to use
the function git_commit_non_empty_tree "$@" instead of the
git commit-tree "$@" idiom in your commit filter to make that
happen.
--original <namespace>
Use this option to set the namespace where the original
commits will be stored. The default value is refs/original.
-d <directory>
Use this option to set the path to the temporary
directory used for rewriting. When applying a tree filter, the command needs
to temporarily check out the tree to some directory, which may consume
considerable space in case of large projects. By default it does this in the
.git-rewrite/ directory but you can override that choice by this
parameter.
-f, --force
git filter-branch refuses to start with an
existing temporary directory or when there are already refs starting with
refs/original/, unless forced.
<rev-list options>...
Arguments for git rev-list. All positive refs
included by these options are rewritten. You may also specify options such as
--all, but you must use -- to separate them from the git
filter-branch options. Implies the section called “Remap to
ancestor”.
Remap to ancestor¶
By using rev-list(1) arguments, e.g., path limiters, you can limit the set of revisions which get rewritten. However, positive refs on the command line are distinguished: we don’t let them be excluded by such limiters. For this purpose, they are instead rewritten to point at the nearest ancestor that was not excluded.EXAMPLES¶
Suppose you want to remove a file (containing confidential information or copyright violation) from all commits:git filter-branch --tree-filter 'rm filename' HEAD
git filter-branch --index-filter 'git rm --cached --ignore-unmatch filename' HEAD
git filter-branch --subdirectory-filter foodir -- --all
git filter-branch --parent-filter 'sed "s/^\$/-p <graft-id>/"' HEAD
git filter-branch --parent-filter \ 'test $GIT_COMMIT = <commit-id> && echo "-p <graft-id>" || cat' HEAD
echo "$commit-id $graft-id" >> .git/info/grafts git filter-branch $graft-id..HEAD
git filter-branch --commit-filter ' if [ "$GIT_AUTHOR_NAME" = "Darl McBribe" ]; then skip_commit "$@"; else git commit-tree "$@"; fi' HEAD
skip_commit() { shift; while [ -n "$1" ]; do shift; map "$1"; shift; done; }
git filter-branch --msg-filter ' sed -e "/^git-svn-id:/d" '
git filter-branch --msg-filter ' cat && echo "Acked-by: Bugs Bunny <bunny@bugzilla.org>" ' HEAD~10..HEAD
git filter-branch --env-filter ' if test "$GIT_AUTHOR_EMAIL" = "root@localhost" then GIT_AUTHOR_EMAIL=john@example.com export GIT_AUTHOR_EMAIL fi if test "$GIT_COMMITTER_EMAIL" = "root@localhost" then GIT_COMMITTER_EMAIL=john@example.com export GIT_COMMITTER_EMAIL fi ' -- --all
D--E--F--G--H / / A--B-----C
git filter-branch ... C..H
git filter-branch ... C..H --not D git filter-branch ... D..H --not C
git filter-branch --index-filter \ 'git ls-files -s | sed "s-\t\"*-&newsubdir/-" | GIT_INDEX_FILE=$GIT_INDEX_FILE.new \ git update-index --index-info && mv "$GIT_INDEX_FILE.new" "$GIT_INDEX_FILE"' HEAD
CHECKLIST FOR SHRINKING A REPOSITORY¶
git-filter-branch can be used to get rid of a subset of files, usually with some combination of --index-filter and --subdirectory-filter. People expect the resulting repository to be smaller than the original, but you need a few more steps to actually make it smaller, because Git tries hard not to lose your objects until you tell it to. First make sure that:•You really removed all variants of a filename, if
a blob was moved over its lifetime. git log --name-only --follow --all --
filename can help you find renames.
•You really filtered all refs: use
--tag-name-filter cat -- --all when calling git-filter-branch.
Then there are two ways to get a smaller repository. A safer way is to clone,
that keeps your original intact.
•Clone it with git clone file:///path/to/repo. The
clone will not have the removed objects. See git-clone(1). (Note that
cloning with a plain path just hardlinks everything!)
If you really don’t want to clone it, for whatever reasons, check the
following points instead (in this order). This is a very destructive approach,
so make a backup or go back to cloning it. You have been warned.
•Remove the original refs backed up by
git-filter-branch: say git for-each-ref --format="%(refname)"
refs/original/ | xargs -n 1 git update-ref -d.
•Expire all reflogs with git reflog expire
--expire=now --all.
•Garbage collect all unreferenced objects with git
gc --prune=now (or if your git-gc is not new enough to support arguments to
--prune, use git repack -ad; git prune instead).
NOTES¶
git-filter-branch allows you to make complex shell-scripted rewrites of your Git history, but you probably don’t need this flexibility if you’re simply removing unwanted data like large files or passwords. For those operations you may want to consider The BFG Repo-Cleaner[1], a JVM-based alternative to git-filter-branch, typically at least 10-50x faster for those use-cases, and with quite different characteristics:•Any particular version of a file is cleaned
exactly once. The BFG, unlike git-filter-branch, does not give you the
opportunity to handle a file differently based on where or when it was
committed within your history. This constraint gives the core performance
benefit of The BFG, and is well-suited to the task of cleansing bad data - you
don’t care where the bad data is, you just want it
gone.
•By default The BFG takes full advantage of
multi-core machines, cleansing commit file-trees in parallel.
git-filter-branch cleans commits sequentially (ie in a single-threaded
manner), though it is possible to write filters that include their own
parallellism, in the scripts executed against each commit.
•The command options[2] are much more
restrictive than git-filter branch, and dedicated just to the tasks of
removing unwanted data- e.g: --strip-blobs-bigger-than 1M.
GIT¶
Part of the git(1) suiteNOTES¶
- 1.
- The BFG Repo-Cleaner
- 2.
- command options
05/28/2018 | Git 2.1.4 |