DESCRIPTION
-----------
-Lets you rewrite git revision history by rewriting the branches mentioned
+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.
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,
+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
' 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 "$GIT_AUTHOR_EMAIL" = "root@localhost"
+ then
+ GIT_AUTHOR_EMAIL=john@example.com
+ export GIT_AUTHOR_EMAIL
+ fi
+ if test "$GIT_COMMITTER_EMAIL" = "root@localhost"
+ then
+ GIT_COMMITTER_EMAIL=john@example.com
+ export GIT_COMMITTER_EMAIL
+ fi
+' -- --all
+--------------------------------------------------------
+
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
Checklist for Shrinking a Repository
------------------------------------
-git-filter-branch is often used to get rid of a subset of files,
+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
+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
(or if your git-gc is not new enough to support arguments to
`--prune`, use `git repack -ad; git prune` instead).
+Notes
+-----
+
+git-filter-branch allows you to make complex shell-scripted rewrites
+of your Git history, but you probably don't need this flexibility if
+you're simply _removing unwanted data_ like large files or passwords.
+For those operations you may want to consider
+link:http://rtyley.github.io/bfg-repo-cleaner/[The BFG Repo-Cleaner],
+a JVM-based alternative to git-filter-branch, typically at least
+10-50x faster for those use-cases, and with quite different
+characteristics:
+
+* Any particular version of a file is cleaned exactly _once_. The BFG,
+ unlike git-filter-branch, does not give you the opportunity to
+ handle a file differently based on where or when it was committed
+ within your history. This constraint gives the core performance
+ benefit of The BFG, and is well-suited to the task of cleansing bad
+ data - you don't care _where_ the bad data is, you just want it
+ _gone_.
+
+* By default The BFG takes full advantage of multi-core machines,
+ cleansing commit file-trees in parallel. git-filter-branch cleans
+ commits sequentially (ie in a single-threaded manner), though it
+ _is_ possible to write filters that include their own parallellism,
+ in the scripts executed against each commit.
+
+* The link:http://rtyley.github.io/bfg-repo-cleaner/#examples[command options]
+ are much more restrictive than git-filter branch, and dedicated just
+ to the tasks of removing unwanted data- e.g:
+ `--strip-blobs-bigger-than 1M`.
+
GIT
---
Part of the linkgit:git[1] suite