GIT-FILTER-BRANCH(1)GIT-FILTER-BRANCH(1)NAMEgit-filter-branch - Rewrite branches
SYNOPSIS
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 men-
tioned in the <rev-list options>, applying custom filters on each revi-
sion. Those filters can modify each tree (e.g. removing a file or run-
ning 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 com-
mand 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, there-
fore such a usage is permitted.
NOTE: This command honors .git/info/grafts. If you have any grafts
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 sin-
gle 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.
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GIT-FILTER-BRANCH(1)GIT-FILTER-BRANCH(1)
Filters
The filters are applied in the order as listed below. The <command>
argument is always evaluated in the shell context using the eval com-
mand (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 set according to the
current commit. The values of these variables after the filters have
run, are used for the new commit. 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 mul-
tiple commits.
OPTIONS--env-filter <command>
This filter may be used if you only need to modify the environ-
ment in which the commit will be performed. Specifically, you
might want to rewrite the author/committer name/email/time envi-
ronment 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.
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GIT-FILTER-BRANCH(1)GIT-FILTER-BRANCH(1)--msg-filter <command>
This is the filter for rewriting the commit messages. The argu-
ment 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 com-
mand, with arguments of the form "<TREE_ID> [(-p <PARENT_COM-
MIT_ID>)...]" and the log message on stdin. The commit id is
expected on stdout.
As a special extension, the commit filter may emit multiple com-
mit 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_com-
mit "$@" 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 signa-
ture attached, the signature will be stripped. It is by defini-
tion 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.
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GIT-FILTER-BRANCH(1)GIT-FILTER-BRANCH(1)--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 [xref to refsect2].
--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 --com-
mit-filter. Though you just need to use the function git_com-
mit_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 con-
sume 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 fil-
ter-branch options. Implies [xref to refsect2].
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
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GIT-FILTER-BRANCH(1)GIT-FILTER-BRANCH(1)
or copyright violation) from all commits:
.ft C
git filter-branch --tree-filter 'rm filename' HEAD
.ft
However, if the file is absent from the tree of some commit, a simple
rm filename will fail for that tree and commit. Thus you may instead
want to use rm -f filename as the script.
Using \--index-filter with git rm yields a significantly faster ver-
sion. Like with using rm filename, git rm --cached filename will fail
if the file is absent from the tree of a commit. If you want to "com-
pletely forget" a file, it does not matter when it entered history, so
we also add \--ignore-unmatch:
.ft C
git filter-branch --index-filter 'git rm --cached --ignore-unmatch filename' HEAD
.ft
Now, you will get the rewritten history saved in HEAD.
To rewrite the repository to look as if foodir/ had been its project
root, and discard all other history:
.ft C
git filter-branch --subdirectory-filter foodir -- --all
.ft
Thus you can, e.g., turn a library subdirectory into a repository of
its own. Note the \-- that separates filter-branch options from revi-
sion options, and the \--all to rewrite all branches and tags.
To set a commit (which typically is at the tip of another history) to
be the parent of the current initial commit, in order to paste the
other history behind the current history:
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GIT-FILTER-BRANCH(1)GIT-FILTER-BRANCH(1)
.ft C
git filter-branch --parent-filter 'sed "s/^\$/-p <graft-id>/"' HEAD
.ft
(if the parent string is empty - which happens when we are dealing with
the initial commit - add graftcommit as a parent). Note that this
assumes history with a single root (that is, no merge without common
ancestors happened). If this is not the case, use:
.ft C
git filter-branch --parent-filter \
'test $GIT_COMMIT = <commit-id> && echo "-p <graft-id>" || cat' HEAD
.ft
or even simpler:
.ft C
echo "$commit-id $graft-id" >> .git/info/grafts
git filter-branch $graft-id..HEAD
.ft
To remove commits authored by "Darl McBribe" from the history:
.ft C
git filter-branch --commit-filter '
if [ "$GIT_AUTHOR_NAME" = "Darl McBribe" ];
then
skip_commit "$@";
else
git commit-tree "$@";
fi' HEAD
.ft
The function skip_commit is defined as follows:
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GIT-FILTER-BRANCH(1)GIT-FILTER-BRANCH(1)
.ft C
skip_commit()
{
shift;
while [ -n "$1" ];
do
shift;
map "$1";
shift;
done;
}
.ft
The shift magic first throws away the tree id and then the -p parame-
ters. Note that this handles merges properly! In case Darl committed a
merge between P1 and P2, it will be propagated properly and all chil-
dren of the merge will become merge commits with P1,P2 as their parents
instead of the merge commit.
You can rewrite the commit log messages using --msg-filter. For exam-
ple, git svn-id strings in a repository created by git svn can be
removed this way:
.ft C
git filter-branch --msg-filter '
sed -e "/^git-svn-id:/d"
.ft
To restrict rewriting to only part of the history, specify a revision
range in addition to the new branch name. The new branch name will
point to the top-most revision that a git rev-list of this range will
print.
If you need to add Acked-by lines to, say, the last 10 commits (none of
which is a merge), use this command:
.ft C
git filter-branch --msg-filter '
cat &&
echo "Acked-by: Bugs Bunny <bunny@bugzilla.org>"
.ft
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GIT-FILTER-BRANCH(1)GIT-FILTER-BRANCH(1)
NOTE the changes introduced by the commits, and which are not reverted
by subsequent commits, will still be in the rewritten branch. If you
want to throw out changes together with the commits, you should use the
interactive mode of git rebase.
Consider this history:
.ft C
D--E--F--G--H
/ /
A--B-----C
.ft
To rewrite only commits D,E,F,G,H, but leave A, B and C alone, use:
.ft C
git filter-branch ... C..H
.ft
To rewrite commits E,F,G,H, use one of these:
.ft C
git filter-branch ... C..H --not D
git filter-branch ... D..H --not C
.ft
To move the whole tree into a subdirectory, or remove it from there:
.ft C
git filter-branch --index-filter \
'git ls-files -s | sed "s-\t\"*-&newsubdir/-" |
GIT_INDEX_FILE=$GIT_INDEX_FILE.new \
git update-index --index-info &&
mv $GIT_INDEX_FILE.new $GIT_INDEX_FILE' HEAD
.ft
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GIT-FILTER-BRANCH(1)GIT-FILTER-BRANCH(1)CHECKLIST FOR SHRINKING A REPOSITORYgit-filter-branch is often used to get rid of a subset of files, usu-
ally with some combination of \--index-filter and \--subdirectory-fil-
ter. 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:
o You really removed all variants of a filename, if a blob was moved
over its lifetime. git log \--name-only \--follow \--all \-- file-
name can help you find renames.
o 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.
o 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 destruc-
tive approach, so make a backup or go back to cloning it. You have been
warned.
o 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.
o Expire all reflogs with git reflog expire \--expire=now \--all.
o 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).
AUTHOR
Written by Petr "Pasky" Baudis <pasky@suse.cz: mailto:pasky@suse.cz>,
and the git list <git@vger.kernel.org: mailto:git@vger.kernel.org>
DOCUMENTATION
Documentation by Petr Baudis and the git list.
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GIT-FILTER-BRANCH(1)GIT-FILTER-BRANCH(1)GIT
Part of the git(1) suite
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