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cg-admin-rewritehist

NAME

cg-admin-rewritehist - rewrite revision history

SYNOPSIS

cg-admin-rewritehist [-d TEMPDIR] [-r STARTREV]... [-k KEEPREV]... [FILTERS] DESTBRANCH

DESCRIPTION

Lets you rewrite GIT revision history by creating a new branch from your current branch by 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 takes the new branch name as a mandatory argument and the filters as optional arguments. If you specify no filters, the commits will be recommitted without any changes, which would normally have no effect and result with the new branch pointing to the same branch as your current branch. (Nevertheless, this may be useful in the future for compensating for some Git bugs or such, therefore such a usage is permitted.)

WARNING! The rewritten history will have different ids 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. Please do not use this command if you do not know the full implications, and avoid using it anyway - do not do what a simple single commit on top of the current version would fix.

Always verify that the rewritten version is correct before disposing the original branch.

OPTIONS

-d TEMPDIR

When applying a tree filter, the command needs to temporary checkout 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.

-r STARTREV

Normally, the command will rewrite the entire history. If you pass this argument, though, this will be the first commit it will rewrite and keep the previous commits intact.

-k KEEPREV

If you pass this argument, this commit and all of its predecessors are kept intact.

-h, --help

Print usage summary.

--long-help

Print user manual. The same as found in gitm[blue]1m[][1].

Filters

The filters are applied in the order as listed below. The COMMAND argument is always evaluated in shell using the eval command. The $GIT_COMMIT environment variable is permanently set to contain the id of the commit being rewritten. The author/committer environment variables are set before the first filter is run.

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, fails otherwise; the map function can return several ids on separate lines if your commit filter emitted multiple commits (see below).

--env-filter COMMAND

This is the filter for modifying the environment in which the commit will be performed. Specifically, you might want to rewrite the author/committer name/email/time environment variables (see gitm[blue]1m[][2] 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 COMMAND 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 - .gitignore files nor any other ignore rules HAVE NO EFFECT!).

--index-filter COMMAND

This is the filter for rewriting the Git's directory index. It is similar to the tree filter but does not check out the tree, which makes it much faster. However, you must use the lowlevel Git index manipulation commands to do your work.

--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 format accepted by git-commit-tree: empty for 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 COMMAND argument is evaluated in shell with the original commit message on standard input; its standard output is is used as the new commit message.

--commit-filter COMMAND

If this filter is passed, it will be called instead of the git-commit-tree command, with those arguments:

 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, all of them will be used
 as parents instead of the original commit in further commits.
 

EXAMPLE USAGE

Suppose you want to remove a file (containing confidential information or copyright violation) from all commits:

 cg-admin-rewritehist --tree-filter 'rm filename' newbranch
 

A significantly faster version:

 cg-admin-rewritehist --index-filter 'git-update-index --remove filename' newbranch
 

Now, you will get the rewritten history saved in the branch newbranch (your current branch is left untouched).

To "etch-graft" a commit to the revision history (set a commit to be the parent of the current initial commit and propagate that):

 cg-admin-rewritehist --parent-filter sed\ 's/^$/-p graftcommitid/' newbranch
 

(if the parent string is empty - therefore we are dealing with the initial commit - add graftcommit as a parent). Note that this assumes history with a single root (that is, no cg-merge -j happened). If this is not the case, use:

 cg-admin-rewritehist --parent-filter 'cat; [ "$GIT_COMMIT" = "COMMIT" ] && echo "-p GRAFTCOMMIT"' newbranch
 

To remove commits authored by "Darl McBribe" from the history:

 cg-admin-rewritehist --commit-filter 'if [ "$GIT_AUTHOR_NAME" = "Darl McBribe" ]; then shift; while [ -n "$1" ]; do shift; echo "$1"; shift; done; else git-commit-tree "$@"; fi' newbranch
 

(the shift magic first throws away the tree id and then the -p parameters). Note that this handles merges properly! In case Darl committed a merge between P1 and P2, it will be propagated properly and all children of the merge will become merge commits with P1,P2 as their parents instead of the merge commit.

To restrict rewriting to only part of the history, use -r or -k or both. Consider this history:

      D--E--F--G--H
     /     /
 A--B-----C
 

To rewrite only commits F,G,H, use:

 cg-admin-rewritehist -r F ...
 

To rewrite commits E,F,G,H, use one of these:

 cg-admin-rewritehist -r E -k C ...
 cg-admin-rewritehist -k D -k C ...
 

COPYRIGHT

Copyright © Petr Baudis, 2006

SEE ALSO

cg-admin-rewritehist is part of gitm[blue]7m[][3], a toolkit for managing gitm[blue]7m[][4] trees.

NOTES

1.

1

[set $man.base.url.for.relative.links]/cg-admin-rewritehist

2.

1

[set $man.base.url.for.relative.links]/cg-commit

3.

7

[set $man.base.url.for.relative.links]/cogito

4.

7

[set $man.base.url.for.relative.links]/git