# git-filter-branch

## NAME



           git-filter-branch - Rewrite branches
    


## SYNOPSIS



           _git filter-branch_ [--setup <command>] [--subdirectory-filter <directory>]
                   [--env-filter <command>] [--tree-filter <command>]
                   [--index-filter <command>] [--parent-filter <command>]
                   [--msg-filter <command>] [--commit-filter <command>]
                   [--tag-name-filter <command>] [--prune-empty]
                   [--original <namespace>] [-d <directory>] [-f | --force]
                   [--state-branch <branch>] [--] [<rev-list-options>...]
    


## WARNING



           _git filter-branch_ has a plethora of pitfalls that can produce
           non-obvious manglings of the intended history rewrite (and can
           leave you with little time to investigate such problems since it
           has such abysmal performance). These safety and performance issues
           cannot be backward compatibly fixed and as such, its use is not
           recommended. Please use an alternative history filtering tool such
           as **git filter-repo******[1]. If you still need to use _git filter-branch_ ,
           please carefully read the section called “SAFETY” (and the section
           called “PERFORMANCE”) to learn about the land mines of
           filter-branch, and then vigilantly avoid as many of the hazards
           listed there as reasonably possible.
    


## 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



           --setup <command>
               This is not a real filter executed for each commit but a one
               time setup just before the loop. Therefore no commit-specific
               variables are defined yet. Functions or variables defined here
               can be used or modified in the following filter steps except
               the commit filter, for technical reasons.
    
           --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”.
    
           --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).
    
           --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.
    
           --prune-empty
               Some filters will generate empty commits that leave the tree
               untouched. This option instructs git-filter-branch to remove
               such commits if they have exactly one or zero non-pruned
               parents; merge commits will therefore remain intact. This
               option cannot be used together with **--commit-filter** , though
               the same effect can be achieved by using the provided
               **git_commit_non_empty_tree** function in a commit filter.
    
           --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.
    
           --state-branch <branch>
               This option will cause the mapping from old to new objects to
               be loaded from named branch upon startup and saved as a new
               commit to that branch upon exit, enabling incremental of large
               trees. If _< branch>_ does not exist it will be created.
    
           <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 git-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.
    


## EXIT STATUS



           On success, the exit status is **0**. If the filter can’t find any
           commits to rewrite, the exit status is **2**. On any other error, the
           exit status may be any other non-zero value.
    


## 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
    
           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
           version. 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 "completely forget" a file, it does not matter when it
           entered history, so we also add **--ignore-unmatch** :
    
               git filter-branch --index-filter 'git rm --cached --ignore-unmatch filename' HEAD
    
           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:
    
               git filter-branch --subdirectory-filter foodir -- --all
    
           Thus you can, e.g., turn a library subdirectory into a repository
           of its own. Note the **--** that separates _filter-branch_ options from
           revision 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:
    
               git filter-branch --parent-filter 'sed "s/^\$/-p <graft-id>/"' HEAD
    
           (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:
    
               git filter-branch --parent-filter \
                       'test $GIT_COMMIT = <commit-id> && echo "-p <graft-id>" || cat' HEAD
    
           or even simpler:
    
               git replace --graft $commit-id $graft-id
               git filter-branch $graft-id..HEAD
    
           To remove commits authored by "Darl McBribe" from the history:
    
               git filter-branch --commit-filter '
                       if [ "$GIT_AUTHOR_NAME" = "Darl McBribe" ];
                       then
                               skip_commit "$@";
                       else
                               git commit-tree "$@";
                       fi' HEAD
    
           The function _skip_commit_ is defined as follows:
    
               skip_commit()
               {
                       shift;
                       while [ -n "$1" ];
                       do
                               shift;
                               map "$1";
                               shift;
                       done;
               }
    
           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.
    
           **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_.
    
           You can rewrite the commit log messages using **--msg-filter**. For
           example, _git svn-id_ strings in a repository created by _git svn_ can
           be removed this way:
    
               git filter-branch --msg-filter '
                       sed -e "/^git-svn-id:/d"
               '
    
           If you need to add _Acked-by_ lines to, say, the last 10 commits
           (none of which is a merge), use this command:
    
               git filter-branch --msg-filter '
                       cat &&
                       echo "Acked-by: Bugs Bunny <bunny@bugzilla.org>"
               ' HEAD~10..HEAD
    
           The **--env-filter** option can be used to modify committer and/or
           author identity. For example, if you found out that your commits
           have the wrong identity due to a misconfigured user.email, you can
           make a correction, before publishing the project, like this:
    
               git filter-branch --env-filter '
                       if test "$GIT_AUTHOR_EMAIL" = "root@localhost"
                       then
                               GIT_AUTHOR_EMAIL=john@example.com
                       fi
                       if test "$GIT_COMMITTER_EMAIL" = "root@localhost"
                       then
                               GIT_COMMITTER_EMAIL=john@example.com
                       fi
               ' -- --all
    
           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.
    
           Consider this history:
    
                    D--E--F--G--H
                   /     /
               A--B-----C
    
           To rewrite only commits D,E,F,G,H, but leave A, B and C alone,
           use:
    
               git filter-branch ... C..H
    
           To rewrite commits E,F,G,H, use one of these:
    
               git filter-branch ... C..H --not D
               git filter-branch ... D..H --not C
    
           To move the whole tree into a subdirectory, or remove it from
           there:
    
               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).
    


## PERFORMANCE



           The performance of git-filter-branch is glacially slow; its design
           makes it impossible for a backward-compatible implementation to
           ever be fast:
    
           •   In editing files, git-filter-branch by design checks out each
               and every commit as it existed in the original repo. If your
               repo has **10^5** files and **10^5** commits, but each commit only
               modifies five files, then git-filter-branch will make you do
               **10^10** modifications, despite only having (at most) **5*10^5**
               unique blobs.
    
           •   If you try and cheat and try to make git-filter-branch only
               work on files modified in a commit, then two things happen
    
               •   you run into problems with deletions whenever the user is
                   simply trying to rename files (because attempting to
                   delete files that don’t exist looks like a no-op; it takes
                   some chicanery to remap deletes across file renames when
                   the renames happen via arbitrary user-provided shell)
    
               •   even if you succeed at the map-deletes-for-renames
                   chicanery, you still technically violate backward
                   compatibility because users are allowed to filter files in
                   ways that depend upon topology of commits instead of
                   filtering solely based on file contents or names (though
                   this has not been observed in the wild).
    
           •   Even if you don’t need to edit files but only want to e.g.
               rename or remove some and thus can avoid checking out each
               file (i.e. you can use --index-filter), you still are passing
               shell snippets for your filters. This means that for every
               commit, you have to have a prepared git repo where those
               filters can be run. That’s a significant setup.
    
           •   Further, several additional files are created or updated per
               commit by git-filter-branch. Some of these are for supporting
               the convenience functions provided by git-filter-branch (such
               as map()), while others are for keeping track of internal
               state (but could have also been accessed by user filters; one
               of git-filter-branch’s regression tests does so). This
               essentially amounts to using the filesystem as an IPC
               mechanism between git-filter-branch and the user-provided
               filters. Disks tend to be a slow IPC mechanism, and writing
               these files also effectively represents a forced
               synchronization point between separate processes that we hit
               with every commit.
    
           •   The user-provided shell commands will likely involve a
               pipeline of commands, resulting in the creation of many
               processes per commit. Creating and running another process
               takes a widely varying amount of time between operating
               systems, but on any platform it is very slow relative to
               invoking a function.
    
           •   git-filter-branch itself is written in shell, which is kind of
               slow. This is the one performance issue that could be
               backward-compatibly fixed, but compared to the above problems
               that are intrinsic to the design of git-filter-branch, the
               language of the tool itself is a relatively minor issue.
    
               •   Side note: Unfortunately, people tend to fixate on the
                   written-in-shell aspect and periodically ask if
                   git-filter-branch could be rewritten in another language
                   to fix the performance issues. Not only does that ignore
                   the bigger intrinsic problems with the design, it’d help
                   less than you’d expect: if git-filter-branch itself were
                   not shell, then the convenience functions (map(),
                   skip_commit(), etc) and the **--setup** argument could no
                   longer be executed once at the beginning of the program
                   but would instead need to be prepended to every user
                   filter (and thus re-executed with every commit).
    
           The **git filter-repo******[1] tool is an alternative to git-filter-branch
           which does not suffer from these performance problems or the
           safety problems (mentioned below). For those with existing tooling
           which relies upon git-filter-branch,_git filter-repo_ also provides
           **filter-lamely******[2], a drop-in git-filter-branch replacement (with a
           few caveats). While filter-lamely suffers from all the same safety
           issues as git-filter-branch, it at least ameliorates the
           performance issues a little.


## SAFETY



           git-filter-branch is riddled with gotchas resulting in various
           ways to easily corrupt repos or end up with a mess worse than what
           you started with:
    
           •   Someone can have a set of "working and tested filters" which
               they document or provide to a coworker, who then runs them on
               a different OS where the same commands are not working/tested
               (some examples in the git-filter-branch manpage are also
               affected by this). BSD vs. GNU userland differences can really
               bite. If lucky, error messages are spewed. But just as likely,
               the commands either don’t do the filtering requested, or
               silently corrupt by making some unwanted change. The unwanted
               change may only affect a few commits, so it’s not necessarily
               obvious either. (The fact that problems won’t necessarily be
               obvious means they are likely to go unnoticed until the
               rewritten history is in use for quite a while, at which point
               it’s really hard to justify another flag-day for another
               rewrite.)
    
           •   Filenames with spaces are often mishandled by shell snippets
               since they cause problems for shell pipelines. Not everyone is
               familiar with find -print0, xargs -0, git-ls-files -z, etc.
               Even people who are familiar with these may assume such flags
               are not relevant because someone else renamed any such files
               in their repo back before the person doing the filtering
               joined the project. And often, even those familiar with
               handling arguments with spaces may not do so just because they
               aren’t in the mindset of thinking about everything that could
               possibly go wrong.
    
           •   Non-ascii filenames can be silently removed despite being in a
               desired directory. Keeping only wanted paths is often done
               using pipelines like **git ls-files** | **grep -v ^WANTED_DIR/** |
               **xargs git rm**. ls-files will 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). Yes, someone
               who knows about core.quotePath can avoid this (unless they
               have other special characters like \t, \n, or "), and people
               who use ls-files -z with something other than grep can avoid
               this, but that doesn’t mean they will.
    
           •   Similarly, when moving files around, one can find that
               filenames with non-ascii or special characters end up in a
               different directory, one 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.)
    
           •   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:
    
               •   the default to only doing a partial history rewrite (_--all_
                   is not the default and few examples show it)
    
               •   the fact that there’s no automatic post-run cleanup
    
               •   the fact that --tag-name-filter (when used to rename tags)
                   doesn’t remove the old tags but just adds new ones with
                   the new name
    
               •   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 "DISCUSSION"
                   section of the git filter-repo manual page for more
                   details.
    
           •   Annotated tags can be accidentally converted to lightweight
               tags, due to either of two issues:
    
               •   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.)
    
               •   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 restored from refs/original/ in a previously botched
                   rewrite).
    
           •   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.)
    
           •   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.
    
           •   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.)
    
           •   If --prune-empty isn’t specified, then the filtering process
               can create hoards of confusing empty commits
    
           •   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.
    
           •   If --prune-empty is specified, sometimes empty commits are
               missed and left around anyway (a somewhat rare bug, but it
               happens...)
    
           •   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.
    
           •   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



           Part of the git(1) suite
    


## NOTES



            1. git filter-repo
               https://github.com/newren/git-filter-repo/
    
            2. filter-lamely
               https://github.com/newren/git-filter-repo/blob/master/contrib/filter-repo-demos/filter-lamely
    


* * *