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694 lines
30 KiB
git-filter-branch(1) |
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==================== |
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|
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NAME |
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---- |
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git-filter-branch - Rewrite branches |
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SYNOPSIS |
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-------- |
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[verse] |
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'git filter-branch' [--setup <command>] [--subdirectory-filter <directory>] |
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[--env-filter <command>] [--tree-filter <command>] |
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[--index-filter <command>] [--parent-filter <command>] |
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[--msg-filter <command>] [--commit-filter <command>] |
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[--tag-name-filter <command>] [--prune-empty] |
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[--original <namespace>] [-d <directory>] [-f | --force] |
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[--state-branch <branch>] [--] [<rev-list options>...] |
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WARNING |
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------- |
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'git filter-branch' has a plethora of pitfalls that can produce non-obvious |
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manglings of the intended history rewrite (and can leave you with little |
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time to investigate such problems since it has such abysmal performance). |
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These safety and performance issues cannot be backward compatibly fixed and |
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as such, its use is not recommended. Please use an alternative history |
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filtering tool such as https://github.com/newren/git-filter-repo/[git |
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filter-repo]. If you still need to use 'git filter-branch', please |
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carefully read <<SAFETY>> (and <<PERFORMANCE>>) to learn about the land |
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mines of filter-branch, and then vigilantly avoid as many of the hazards |
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listed there as reasonably possible. |
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DESCRIPTION |
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----------- |
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Lets you rewrite Git revision history by rewriting the branches mentioned |
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in the <rev-list options>, applying custom filters on each revision. |
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Those filters can modify each tree (e.g. removing a file or running |
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a perl rewrite on all files) or information about each commit. |
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Otherwise, all information (including original commit times or merge |
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information) will be preserved. |
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The command will only rewrite the _positive_ refs mentioned in the |
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command line (e.g. if you pass 'a..b', only 'b' will be rewritten). |
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If you specify no filters, the commits will be recommitted without any |
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changes, which would normally have no effect. Nevertheless, this may be |
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useful in the future for compensating for some Git bugs or such, |
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therefore such a usage is permitted. |
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*NOTE*: This command honors `.git/info/grafts` file and refs in |
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the `refs/replace/` namespace. |
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If you have any grafts or replacement refs defined, running this command |
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will make them permanent. |
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*WARNING*! The rewritten history will have different object names for all |
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the objects and will not converge with the original branch. You will not |
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be able to easily push and distribute the rewritten branch on top of the |
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original branch. Please do not use this command if you do not know the |
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full implications, and avoid using it anyway, if a simple single commit |
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would suffice to fix your problem. (See the "RECOVERING FROM UPSTREAM |
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REBASE" section in linkgit:git-rebase[1] for further information about |
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rewriting published history.) |
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Always verify that the rewritten version is correct: The original refs, |
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if different from the rewritten ones, will be stored in the namespace |
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'refs/original/'. |
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Note that since this operation is very I/O expensive, it might |
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be a good idea to redirect the temporary directory off-disk with the |
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`-d` option, e.g. on tmpfs. Reportedly the speedup is very noticeable. |
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Filters |
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~~~~~~~ |
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The filters are applied in the order as listed below. The <command> |
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argument is always evaluated in the shell context using the 'eval' command |
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(with the notable exception of the commit filter, for technical reasons). |
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Prior to that, the `$GIT_COMMIT` environment variable will be set to contain |
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the id of the commit being rewritten. Also, GIT_AUTHOR_NAME, |
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GIT_AUTHOR_EMAIL, GIT_AUTHOR_DATE, GIT_COMMITTER_NAME, GIT_COMMITTER_EMAIL, |
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and GIT_COMMITTER_DATE are taken from the current commit and exported to |
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the environment, in order to affect the author and committer identities of |
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the replacement commit created by linkgit:git-commit-tree[1] after the |
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filters have run. |
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If any evaluation of <command> returns a non-zero exit status, the whole |
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operation will be aborted. |
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A 'map' function is available that takes an "original sha1 id" argument |
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and outputs a "rewritten sha1 id" if the commit has been already |
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rewritten, and "original sha1 id" otherwise; the 'map' function can |
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return several ids on separate lines if your commit filter emitted |
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multiple commits. |
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OPTIONS |
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------- |
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--setup <command>:: |
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This is not a real filter executed for each commit but a one |
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time setup just before the loop. Therefore no commit-specific |
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variables are defined yet. Functions or variables defined here |
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can be used or modified in the following filter steps except |
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the commit filter, for technical reasons. |
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--subdirectory-filter <directory>:: |
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Only look at the history which touches the given subdirectory. |
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The result will contain that directory (and only that) as its |
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project root. Implies <<Remap_to_ancestor>>. |
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--env-filter <command>:: |
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This filter may be used if you only need to modify the environment |
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in which the commit will be performed. Specifically, you might |
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want to rewrite the author/committer name/email/time environment |
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variables (see linkgit:git-commit-tree[1] for details). |
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--tree-filter <command>:: |
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This is the filter for rewriting the tree and its contents. |
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The argument is evaluated in shell with the working |
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directory set to the root of the checked out tree. The new tree |
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is then used as-is (new files are auto-added, disappeared files |
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are auto-removed - neither .gitignore files nor any other ignore |
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rules *HAVE ANY EFFECT*!). |
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--index-filter <command>:: |
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This is the filter for rewriting the index. It is similar to the |
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tree filter but does not check out the tree, which makes it much |
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faster. Frequently used with `git rm --cached |
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--ignore-unmatch ...`, see EXAMPLES below. For hairy |
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cases, see linkgit:git-update-index[1]. |
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--parent-filter <command>:: |
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This is the filter for rewriting the commit's parent list. |
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It will receive the parent string on stdin and shall output |
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the new parent string on stdout. The parent string is in |
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the format described in linkgit:git-commit-tree[1]: empty for |
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the initial commit, "-p parent" for a normal commit and |
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"-p parent1 -p parent2 -p parent3 ..." for a merge commit. |
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--msg-filter <command>:: |
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This is the filter for rewriting the commit messages. |
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The argument is evaluated in the shell with the original |
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commit message on standard input; its standard output is |
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used as the new commit message. |
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--commit-filter <command>:: |
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This is the filter for performing the commit. |
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If this filter is specified, it will be called instead of the |
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'git commit-tree' command, with arguments of the form |
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"<TREE_ID> [(-p <PARENT_COMMIT_ID>)...]" and the log message on |
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stdin. The commit id is expected on stdout. |
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+ |
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As a special extension, the commit filter may emit multiple |
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commit ids; in that case, the rewritten children of the original commit will |
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have all of them as parents. |
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+ |
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You can use the 'map' convenience function in this filter, and other |
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convenience functions, too. For example, calling 'skip_commit "$@"' |
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will leave out the current commit (but not its changes! If you want |
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that, use 'git rebase' instead). |
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+ |
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You can also use the `git_commit_non_empty_tree "$@"` instead of |
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`git commit-tree "$@"` if you don't wish to keep commits with a single parent |
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and that makes no change to the tree. |
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--tag-name-filter <command>:: |
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This is the filter for rewriting tag names. When passed, |
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it will be called for every tag ref that points to a rewritten |
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object (or to a tag object which points to a rewritten object). |
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The original tag name is passed via standard input, and the new |
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tag name is expected on standard output. |
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+ |
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The original tags are not deleted, but can be overwritten; |
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use "--tag-name-filter cat" to simply update the tags. In this |
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case, be very careful and make sure you have the old tags |
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backed up in case the conversion has run afoul. |
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+ |
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Nearly proper rewriting of tag objects is supported. If the tag has |
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a message attached, a new tag object will be created with the same message, |
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author, and timestamp. If the tag has a signature attached, the |
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signature will be stripped. It is by definition impossible to preserve |
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signatures. The reason this is "nearly" proper, is because ideally if |
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the tag did not change (points to the same object, has the same name, etc.) |
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it should retain any signature. That is not the case, signatures will always |
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be removed, buyer beware. There is also no support for changing the |
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author or timestamp (or the tag message for that matter). Tags which point |
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to other tags will be rewritten to point to the underlying commit. |
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--prune-empty:: |
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Some filters will generate empty commits that leave the tree untouched. |
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This option instructs git-filter-branch to remove such commits if they |
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have exactly one or zero non-pruned parents; merge commits will |
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therefore remain intact. This option cannot be used together with |
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`--commit-filter`, though the same effect can be achieved by using the |
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provided `git_commit_non_empty_tree` function in a commit filter. |
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--original <namespace>:: |
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Use this option to set the namespace where the original commits |
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will be stored. The default value is 'refs/original'. |
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-d <directory>:: |
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Use this option to set the path to the temporary directory used for |
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rewriting. When applying a tree filter, the command needs to |
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temporarily check out the tree to some directory, which may consume |
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considerable space in case of large projects. By default it |
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does this in the `.git-rewrite/` directory but you can override |
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that choice by this parameter. |
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-f:: |
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--force:: |
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'git filter-branch' refuses to start with an existing temporary |
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directory or when there are already refs starting with |
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'refs/original/', unless forced. |
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--state-branch <branch>:: |
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This option will cause the mapping from old to new objects to |
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be loaded from named branch upon startup and saved as a new |
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commit to that branch upon exit, enabling incremental of large |
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trees. If '<branch>' does not exist it will be created. |
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<rev-list options>...:: |
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Arguments for 'git rev-list'. All positive refs included by |
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these options are rewritten. You may also specify options |
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such as `--all`, but you must use `--` to separate them from |
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the 'git filter-branch' options. Implies <<Remap_to_ancestor>>. |
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[[Remap_to_ancestor]] |
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Remap to ancestor |
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~~~~~~~~~~~~~~~~~ |
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By using linkgit:git-rev-list[1] arguments, e.g., path limiters, you can limit the |
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set of revisions which get rewritten. However, positive refs on the command |
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line are distinguished: we don't let them be excluded by such limiters. For |
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this purpose, they are instead rewritten to point at the nearest ancestor that |
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was not excluded. |
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EXIT STATUS |
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----------- |
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On success, the exit status is `0`. If the filter can't find any commits to |
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rewrite, the exit status is `2`. On any other error, the exit status may be |
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any other non-zero value. |
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EXAMPLES |
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-------- |
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Suppose you want to remove a file (containing confidential information |
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or copyright violation) from all commits: |
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------------------------------------------------------- |
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git filter-branch --tree-filter 'rm filename' HEAD |
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------------------------------------------------------- |
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However, if the file is absent from the tree of some commit, |
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a simple `rm filename` will fail for that tree and commit. |
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Thus you may instead want to use `rm -f filename` as the script. |
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Using `--index-filter` with 'git rm' yields a significantly faster |
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version. Like with using `rm filename`, `git rm --cached filename` |
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will fail if the file is absent from the tree of a commit. If you |
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want to "completely forget" a file, it does not matter when it entered |
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history, so we also add `--ignore-unmatch`: |
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-------------------------------------------------------------------------- |
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git filter-branch --index-filter 'git rm --cached --ignore-unmatch filename' HEAD |
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-------------------------------------------------------------------------- |
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Now, you will get the rewritten history saved in HEAD. |
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To rewrite the repository to look as if `foodir/` had been its project |
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root, and discard all other history: |
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------------------------------------------------------- |
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git filter-branch --subdirectory-filter foodir -- --all |
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------------------------------------------------------- |
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Thus you can, e.g., turn a library subdirectory into a repository of |
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its own. Note the `--` that separates 'filter-branch' options from |
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revision options, and the `--all` to rewrite all branches and tags. |
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To set a commit (which typically is at the tip of another |
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history) to be the parent of the current initial commit, in |
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order to paste the other history behind the current history: |
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------------------------------------------------------------------- |
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git filter-branch --parent-filter 'sed "s/^\$/-p <graft-id>/"' HEAD |
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------------------------------------------------------------------- |
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(if the parent string is empty - which happens when we are dealing with |
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the initial commit - add graftcommit as a parent). Note that this assumes |
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history with a single root (that is, no merge without common ancestors |
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happened). If this is not the case, use: |
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-------------------------------------------------------------------------- |
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git filter-branch --parent-filter \ |
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'test $GIT_COMMIT = <commit-id> && echo "-p <graft-id>" || cat' HEAD |
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-------------------------------------------------------------------------- |
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or even simpler: |
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----------------------------------------------- |
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git replace --graft $commit-id $graft-id |
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git filter-branch $graft-id..HEAD |
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----------------------------------------------- |
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To remove commits authored by "Darl McBribe" from the history: |
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------------------------------------------------------------------------------ |
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git filter-branch --commit-filter ' |
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if [ "$GIT_AUTHOR_NAME" = "Darl McBribe" ]; |
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then |
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skip_commit "$@"; |
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else |
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git commit-tree "$@"; |
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fi' HEAD |
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------------------------------------------------------------------------------ |
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The function 'skip_commit' is defined as follows: |
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-------------------------- |
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skip_commit() |
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{ |
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shift; |
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while [ -n "$1" ]; |
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do |
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shift; |
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map "$1"; |
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shift; |
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done; |
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} |
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-------------------------- |
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The shift magic first throws away the tree id and then the -p |
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parameters. Note that this handles merges properly! In case Darl |
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committed a merge between P1 and P2, it will be propagated properly |
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and all children of the merge will become merge commits with P1,P2 |
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as their parents instead of the merge commit. |
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*NOTE* the changes introduced by the commits, and which are not reverted |
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by subsequent commits, will still be in the rewritten branch. If you want |
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to throw out _changes_ together with the commits, you should use the |
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interactive mode of 'git rebase'. |
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You can rewrite the commit log messages using `--msg-filter`. For |
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example, 'git svn-id' strings in a repository created by 'git svn' can |
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be removed this way: |
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------------------------------------------------------- |
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git filter-branch --msg-filter ' |
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sed -e "/^git-svn-id:/d" |
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' |
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------------------------------------------------------- |
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If you need to add 'Acked-by' lines to, say, the last 10 commits (none |
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of which is a merge), use this command: |
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-------------------------------------------------------- |
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git filter-branch --msg-filter ' |
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cat && |
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echo "Acked-by: Bugs Bunny <bunny@bugzilla.org>" |
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' HEAD~10..HEAD |
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-------------------------------------------------------- |
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The `--env-filter` option can be used to modify committer and/or author |
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identity. For example, if you found out that your commits have the wrong |
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identity due to a misconfigured user.email, you can make a correction, |
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before publishing the project, like this: |
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-------------------------------------------------------- |
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git filter-branch --env-filter ' |
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if test "$GIT_AUTHOR_EMAIL" = "root@localhost" |
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then |
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GIT_AUTHOR_EMAIL=john@example.com |
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fi |
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if test "$GIT_COMMITTER_EMAIL" = "root@localhost" |
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then |
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GIT_COMMITTER_EMAIL=john@example.com |
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fi |
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' -- --all |
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-------------------------------------------------------- |
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To restrict rewriting to only part of the history, specify a revision |
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range in addition to the new branch name. The new branch name will |
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point to the top-most revision that a 'git rev-list' of this range |
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will print. |
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Consider this history: |
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------------------ |
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D--E--F--G--H |
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/ / |
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A--B-----C |
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------------------ |
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To rewrite only commits D,E,F,G,H, but leave A, B and C alone, use: |
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-------------------------------- |
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git filter-branch ... C..H |
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-------------------------------- |
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To rewrite commits E,F,G,H, use one of these: |
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---------------------------------------- |
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git filter-branch ... C..H --not D |
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git filter-branch ... D..H --not C |
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---------------------------------------- |
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To move the whole tree into a subdirectory, or remove it from there: |
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--------------------------------------------------------------- |
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git filter-branch --index-filter \ |
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'git ls-files -s | sed "s-\t\"*-&newsubdir/-" | |
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GIT_INDEX_FILE=$GIT_INDEX_FILE.new \ |
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git update-index --index-info && |
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mv "$GIT_INDEX_FILE.new" "$GIT_INDEX_FILE"' HEAD |
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--------------------------------------------------------------- |
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CHECKLIST FOR SHRINKING A REPOSITORY |
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------------------------------------ |
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git-filter-branch can be used to get rid of a subset of files, |
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usually with some combination of `--index-filter` and |
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`--subdirectory-filter`. People expect the resulting repository to |
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be smaller than the original, but you need a few more steps to |
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actually make it smaller, because Git tries hard not to lose your |
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objects until you tell it to. First make sure that: |
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|
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* You really removed all variants of a filename, if a blob was moved |
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over its lifetime. `git log --name-only --follow --all -- filename` |
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can help you find renames. |
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|
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* You really filtered all refs: use `--tag-name-filter cat -- --all` |
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when calling git-filter-branch. |
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Then there are two ways to get a smaller repository. A safer way is |
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to clone, that keeps your original intact. |
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|
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* Clone it with `git clone file:///path/to/repo`. The clone |
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will not have the removed objects. See linkgit:git-clone[1]. (Note |
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that cloning with a plain path just hardlinks everything!) |
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If you really don't want to clone it, for whatever reasons, check the |
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following points instead (in this order). This is a very destructive |
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approach, so *make a backup* or go back to cloning it. You have been |
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warned. |
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* Remove the original refs backed up by git-filter-branch: say `git |
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for-each-ref --format="%(refname)" refs/original/ | xargs -n 1 git |
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update-ref -d`. |
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* Expire all reflogs with `git reflog expire --expire=now --all`. |
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* Garbage collect all unreferenced objects with `git gc --prune=now` |
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(or if your git-gc is not new enough to support arguments to |
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`--prune`, use `git repack -ad; git prune` instead). |
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[[PERFORMANCE]] |
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PERFORMANCE |
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----------- |
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|
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The performance of git-filter-branch is glacially slow; its design makes it |
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impossible for a backward-compatible implementation to ever be fast: |
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|
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* In editing files, git-filter-branch by design checks out each and |
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every commit as it existed in the original repo. If your repo has 10\^5 |
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files and 10\^5 commits, but each commit only modifies 5 files, then |
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git-filter-branch will make you do 10\^10 modifications, despite only |
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having (at most) 5*10^5 unique blobs. |
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* If you try and cheat and try to make git-filter-branch only work on |
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files modified in a commit, then two things happen |
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** you run into problems with deletions whenever the user is simply |
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trying to rename files (because attempting to delete files that |
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don't exist looks like a no-op; it takes some chicanery to remap |
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deletes across file renames when the renames happen via arbitrary |
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user-provided shell) |
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|
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** even if you succeed at the map-deletes-for-renames chicanery, you |
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still technically violate backward compatibility because users are |
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allowed to filter files in ways that depend upon topology of |
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commits instead of filtering solely based on file contents or names |
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(though this has not been observed in the wild). |
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|
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* Even if you don't need to edit files but only want to e.g. rename or |
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remove some and thus can avoid checking out each file (i.e. you can use |
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--index-filter), you still are passing shell snippets for your filters. |
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This means that for every commit, you have to have a prepared git repo |
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where those filters can be run. That's a significant setup. |
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|
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* Further, several additional files are created or updated per commit by |
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git-filter-branch. Some of these are for supporting the convenience |
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functions provided by git-filter-branch (such as map()), while others |
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are for keeping track of internal state (but could have also been |
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accessed by user filters; one of git-filter-branch's regression tests |
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does so). This essentially amounts to using the filesystem as an IPC |
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mechanism between git-filter-branch and the user-provided filters. |
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Disks tend to be a slow IPC mechanism, and writing these files also |
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effectively represents a forced synchronization point between separate |
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processes that we hit with every commit. |
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|
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* The user-provided shell commands will likely involve a pipeline of |
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commands, resulting in the creation of many processes per commit. |
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Creating and running another process takes a widely varying amount of |
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time between operating systems, but on any platform it is very slow |
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relative to invoking a function. |
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|
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* git-filter-branch itself is written in shell, which is kind of slow. |
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This is the one performance issue that could be backward-compatibly |
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fixed, but compared to the above problems that are intrinsic to the |
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design of git-filter-branch, the language of the tool itself is a |
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relatively minor issue. |
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|
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** Side note: Unfortunately, people tend to fixate on the |
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written-in-shell aspect and periodically ask if git-filter-branch |
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could be rewritten in another language to fix the performance |
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issues. Not only does that ignore the bigger intrinsic problems |
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with the design, it'd help less than you'd expect: if |
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git-filter-branch itself were not shell, then the convenience |
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functions (map(), skip_commit(), etc) and the `--setup` argument |
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could no longer be executed once at the beginning of the program |
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but would instead need to be prepended to every user filter (and |
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thus re-executed with every commit). |
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|
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The https://github.com/newren/git-filter-repo/[git filter-repo] tool is |
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an alternative to git-filter-branch which does not suffer from these |
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performance problems or the safety problems (mentioned below). For those |
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with existing tooling which relies upon git-filter-branch, 'git |
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repo-filter' also provides |
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https://github.com/newren/git-filter-repo/blob/master/contrib/filter-repo-demos/filter-lamely[filter-lamely], |
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a drop-in git-filter-branch replacement (with a few caveats). While |
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filter-lamely suffers from all the same safety issues as |
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git-filter-branch, it at least ameloriates the performance issues a |
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little. |
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|
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[[SAFETY]] |
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SAFETY |
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------ |
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|
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git-filter-branch is riddled with gotchas resulting in various ways to |
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easily corrupt repos or end up with a mess worse than what you started |
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with: |
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|
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* Someone can have a set of "working and tested filters" which they |
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document or provide to a coworker, who then runs them on a different OS |
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where the same commands are not working/tested (some examples in the |
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git-filter-branch manpage are also affected by this). BSD vs. GNU |
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userland differences can really bite. If lucky, error messages are |
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spewed. But just as likely, the commands either don't do the filtering |
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requested, or silently corrupt by making some unwanted change. The |
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unwanted change may only affect a few commits, so it's not necessarily |
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obvious either. (The fact that problems won't necessarily be obvious |
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means they are likely to go unnoticed until the rewritten history is in |
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use for quite a while, at which point it's really hard to justify |
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another flag-day for another rewrite.) |
|
|
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* Filenames with spaces are often mishandled by shell snippets since |
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they cause problems for shell pipelines. Not everyone is familiar with |
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find -print0, xargs -0, git-ls-files -z, etc. Even people who are |
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familiar with these may assume such flags are not relevant because |
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someone else renamed any such files in their repo back before the person |
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doing the filtering joined the project. And often, even those familiar |
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with handling arguments with spaces may not do so just because they |
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aren't in the mindset of thinking about everything that could possibly |
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go wrong. |
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|
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* Non-ascii filenames can be silently removed despite being in a desired |
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directory. Keeping only wanted paths is often done using pipelines like |
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`git ls-files | grep -v ^WANTED_DIR/ | xargs git rm`. ls-files will |
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only quote filenames if needed, so folks may not notice that one of the |
|
files didn't match the regex (at least not until it's much too late). |
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Yes, someone who knows about core.quotePath can avoid this (unless they |
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have other special characters like \t, \n, or "), and people who use |
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ls-files -z with something other than grep can avoid this, but that |
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doesn't mean they will. |
|
|
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* Similarly, when moving files around, one can find that filenames with |
|
non-ascii or special characters end up in a different directory, one |
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that includes a double quote character. (This is technically the same |
|
issue as above with quoting, but perhaps an interesting different way |
|
that it can and has manifested as a problem.) |
|
|
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* It's far too easy to accidentally mix up old and new history. It's |
|
still possible with any tool, but git-filter-branch almost invites it. |
|
If lucky, the only downside is users getting frustrated that they don't |
|
know how to shrink their repo and remove the old stuff. If unlucky, |
|
they merge old and new history and end up with multiple "copies" of each |
|
commit, some of which have unwanted or sensitive files and others which |
|
don't. This comes about in multiple different ways: |
|
|
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** the default to only doing a partial history rewrite ('--all' is not |
|
the default and few examples show it) |
|
|
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** the fact that there's no automatic post-run cleanup |
|
|
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** the fact that --tag-name-filter (when used to rename tags) doesn't |
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remove the old tags but just adds new ones with the new name |
|
|
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** the fact that little educational information is provided to inform |
|
users of the ramifications of a rewrite and how to avoid mixing old |
|
and new history. For example, this man page discusses how users |
|
need to understand that they need to rebase their changes for all |
|
their branches on top of new history (or delete and reclone), but |
|
that's only one of multiple concerns to consider. See the |
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"DISCUSSION" section of the git filter-repo manual page for more |
|
details. |
|
|
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* Annotated tags can be accidentally converted to lightweight tags, due |
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to either of two issues: |
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|
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** Someone can do a history rewrite, realize they messed up, restore |
|
from the backups in refs/original/, and then redo their |
|
git-filter-branch command. (The backup in refs/original/ is not a |
|
real backup; it dereferences tags first.) |
|
|
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** Running git-filter-branch with either --tags or --all in your |
|
<rev-list options>. In order to retain annotated tags as |
|
annotated, you must use --tag-name-filter (and must not have |
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restored from refs/original/ in a previously botched rewrite). |
|
|
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* Any commit messages that specify an encoding will become corrupted |
|
by the rewrite; git-filter-branch ignores the encoding, takes the original |
|
bytes, and feeds it to commit-tree without telling it the proper |
|
encoding. (This happens whether or not --msg-filter is used.) |
|
|
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* Commit messages (even if they are all UTF-8) by default become |
|
corrupted due to not being updated -- any references to other commit |
|
hashes in commit messages will now refer to no-longer-extant commits. |
|
|
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* There are no facilities for helping users find what unwanted crud they |
|
should delete, which means they are much more likely to have incomplete |
|
or partial cleanups that sometimes result in confusion and people |
|
wasting time trying to understand. (For example, folks tend to just |
|
look for big files to delete instead of big directories or extensions, |
|
and once they do so, then sometime later folks using the new repository |
|
who are going through history will notice a build artifact directory |
|
that has some files but not others, or a cache of dependencies |
|
(node_modules or similar) which couldn't have ever been functional since |
|
it's missing some files.) |
|
|
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* If --prune-empty isn't specified, then the filtering process can |
|
create hoards of confusing empty commits |
|
|
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* If --prune-empty is specified, then intentionally placed empty |
|
commits from before the filtering operation are also pruned instead of |
|
just pruning commits that became empty due to filtering rules. |
|
|
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* If --prune empty is specified, sometimes empty commits are missed |
|
and left around anyway (a somewhat rare bug, but it happens...) |
|
|
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* A minor issue, but users who have a goal to update all names and |
|
emails in a repository may be led to --env-filter which will only update |
|
authors and committers, missing taggers. |
|
|
|
* If the user provides a --tag-name-filter that maps multiple tags to |
|
the same name, no warning or error is provided; git-filter-branch simply |
|
overwrites each tag in some undocumented pre-defined order resulting in |
|
only one tag at the end. (A git-filter-branch regression test requires |
|
this surprising behavior.) |
|
|
|
Also, the poor performance of git-filter-branch often leads to safety |
|
issues: |
|
|
|
* Coming up with the correct shell snippet to do the filtering you want |
|
is sometimes difficult unless you're just doing a trivial modification |
|
such as deleting a couple files. Unfortunately, people often learn if |
|
the snippet is right or wrong by trying it out, but the rightness or |
|
wrongness can vary depending on special circumstances (spaces in |
|
filenames, non-ascii filenames, funny author names or emails, invalid |
|
timezones, presence of grafts or replace objects, etc.), meaning they |
|
may have to wait a long time, hit an error, then restart. The |
|
performance of git-filter-branch is so bad that this cycle is painful, |
|
reducing the time available to carefully re-check (to say nothing about |
|
what it does to the patience of the person doing the rewrite even if |
|
they do technically have more time available). This problem is extra |
|
compounded because errors from broken filters may not be shown for a |
|
long time and/or get lost in a sea of output. Even worse, broken |
|
filters often just result in silent incorrect rewrites. |
|
|
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* To top it all off, even when users finally find working commands, they |
|
naturally want to share them. But they may be unaware that their repo |
|
didn't have some special cases that someone else's does. So, when |
|
someone else with a different repository runs the same commands, they |
|
get hit by the problems above. Or, the user just runs commands that |
|
really were vetted for special cases, but they run it on a different OS |
|
where it doesn't work, as noted above. |
|
|
|
GIT |
|
--- |
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Part of the linkgit:git[1] suite
|
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