This program dumps the given revisions in a form suitable to be piped into git fast-import.
You can use it as a human-readable bundle replacement (see git-bundle(1)), or as a kind of an interactive git filter-branch.
$ git fast-export --all | (cd /empty/repository && git fast-import)
This will export the whole repository and import it into the existing empty repository. Except for reencoding commits that are not in UTF-8, it would be a one-to-one mirror.
$ git fast-export master~5..master | sed "s|refs/heads/master|refs/heads/other|" | git fast-import
This makes a new branch called other from master~5..master (i.e. if master has linear history, it will take the last 5 commits).
Note that this assumes that none of the blobs and commit messages referenced by that revision range contains the string refs/heads/master.
If the --anonymize option is given, git will attempt to remove all identifying information from the repository while still retaining enough of the original tree and history patterns to reproduce some bugs. The goal is that a git bug which is found on a private repository will persist in the anonymized repository, and the latter can be shared with git developers to help solve the bug.
With this option, git will replace all refnames, paths, blob contents, commit and tag messages, names, and email addresses in the output with anonymized data. Two instances of the same string will be replaced equivalently (e.g., two commits with the same author will have the same anonymized author in the output, but bear no resemblance to the original author string). The relationship between commits, branches, and tags is retained, as well as the commit timestamps (but the commit messages and refnames bear no resemblance to the originals). The relative makeup of the tree is retained (e.g., if you have a root tree with 10 files and 3 trees, so will the output), but their names and the contents of the files will be replaced.
If you think you have found a git bug, you can start by exporting an anonymized stream of the whole repository:
$ git fast-export --anonymize --all >anon-stream
Then confirm that the bug persists in a repository created from that stream (many bugs will not, as they really do depend on the exact repository contents):
$ git init anon-repo $ cd anon-repo $ git fast-import <../anon-stream $ ... test your bug ...
If the anonymized repository shows the bug, it may be worth sharing anon-stream along with a regular bug report. Note that the anonymized stream compresses very well, so gzipping it is encouraged. If you want to examine the stream to see that it does not contain any private data, you can peruse it directly before sending. You may also want to try:
$ perl -pe 's/\d+/X/g' <anon-stream | sort -u | less
which shows all of the unique lines (with numbers converted to "X", to collapse "User 0", "User 1", etc into "User X"). This produces a much smaller output, and it is usually easy to quickly confirm that there is no private data in the stream.