On Mac's HFS where git sets core.precomposeUnicode to true automatically
by git init/clone, when a user creates a simple unicode refname (in NFC
format) such as españa:
$ git branch españa
different commands would display the branch name differently. For
example, git branch, git log --decorate, and git fast-export all used
65 73 70 61 c3 b1 61 (or "espa\xc3\xb1a")
(NFC form) while show-ref would use
65 73 70 61 6e cc 83 61 (or "espan\xcc\x83a")
(NFD form). A stress test for git filter-repo was tripped up by this
inconsistency, though digging in I found that the problems could
compound; for example, if the user ran
$ git pack-refs --all
and then tried to check out the branch, they would be met with:
$ git checkout españa
error: pathspec 'españa' did not match any file(s) known to git
$ git checkout españa --
fatal: invalid reference: españa
$ git branch
españa
* master
Note that the user could run the `git branch` command first and copy and
paste the `españa` portion of the output and still see the same two
errors. Also, if the user added --no-prune to the pack-refs command,
then they would see three branches: master, españa, and españa (those
last two are NFC vs. NFD forms, even if they render the same).
Further, if the user had the `españa` branch checked out before
running `git pack-refs --all`, the user would be greeted with (note
that I'm trimming trailing output with an ellipsis):
$ git rev-parse HEAD
fatal: ambiguous argument 'HEAD': unknown revision or path...
$ git status
On branch españa
No commits yet...
Or worse, if the user didn't check this stuff first, running `git
commit` will create a new commit with all changes of all of history
being squashed into it.
In addition to pack-refs, one could also get into this state with
upload-pack or anything that calls either pack-refs or upload-pack (e.g.
gc or clone).
Add code in a few places (pack-refs, show-ref, upload-pack) to check and
honor the setting of core.precomposeUnicode to avoid these bugs.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
8e712ef6fc