git fast-export [<options>] | git fast-import
You can use it as a human-readable bundle replacement (see git-bundle(1)), or as a format that can be edited before being fed to git fast-import in order to do history rewrites (an ability relied on by tools like git filter-repo).
When asking to abort (which is the default), this program will die when encountering a signed tag. With strip, the tags will silently be made unsigned, with warn-strip they will be made unsigned but a warning will be displayed, with verbatim, they will be silently exported and with warn, they will be exported, but you will see a warning.
When asking to abort (which is the default), this program will die when encountering such a tag. With drop it will omit such tags from the output. With rewrite, if the tagged object is a commit, it will rewrite the tag to tag an ancestor commit (via parent rewriting; see git-rev-list(1))
Note that earlier versions of this command did not complain and produced incorrect results if you gave these options.
Any commits (or tags) that have already been marked will not be exported again. If the backend uses a similar --import-marks file, this allows for incremental bidirectional exporting of the repository by keeping the marks the same across runs.
$ 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.
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.
Reproducing some bugs may require referencing particular commits or paths, which becomes challenging after refnames and paths have been anonymized. You can ask for a particular token to be left as-is or mapped to a new value. For example, if you have a bug which reproduces with git rev-list sensitive -- secret.c, you can run:
$ git fast-export --anonymize --all \ --anonymize-map=sensitive:foo \ --anonymize-map=secret.c:bar.c \ >stream
After importing the stream, you can then run git rev-list foo -- bar.c in the anonymized repository.
Note that paths and refnames are split into tokens at slash boundaries. The command above would anonymize subdir/secret.c as something like path123/bar.c; you could then search for bar.c in the anonymized repository to determine the final pathname.
To make referencing the final pathname simpler, you can map each path component; so if you also anonymize subdir to publicdir, then the final pathname would be publicdir/bar.c.