Getting this when a git push to git:// runs the pre-receive hook
which is set up by the `git_test_receive_wrapper`:

	remote: fatal: Not a git repository (or any of the parent directories): .git
	remote: 'git log --pretty=raw --raw --abbrev=40 --always -c -r 21161ba01a093534ef97188eae098d83554dbcc6..73820a1d7e76318d8b1ac23e1c6d47e50a3e8ca2 --no-renames -- .' failed: 
	To git://git-annex.branchable.com/
	 ! [remote rejected]     master -> master (pre-receive hook declined)
	error: failed to push some refs to 'git://git-annex.branchable.com/'

Relevant code:

                # Avoid chdir when running git here, because the changes
                # are in the master git repo, not the srcdir repo.
                # (Also, if a subdir is involved, we don't want to chdir to
                # it and only see changes in it.)
                # The pre-receive hook already puts us in the right place.
                push @rets, git_parse_changes('.', 0, git_commit_info('.', $oldrev."..".$newrev));

This is with  git 1:2.11.0-3+deb9u2 on debian stable, ikiwiki 3.20171002.

Tossing a call to pwd in there, it's at the top of the master (bare) git
repository, which seems right. I can do a similar git log at that location
manually (using different revs). Looking at the environment at that point
(in another wiki that has the same problem), I found only these
git env vars:

	remote: GIT_ALTERNATE_OBJECT_DIRECTORIES=/home/b-joeyh/source.git/./objects
	remote: GIT_OBJECT_DIRECTORY=/home/b-joeyh/source.git/./objects/incoming-hVfXvD
	remote: GIT_QUARANTINE_PATH=/home/b-joeyh/source.git/./objects/incoming-hVfXvD

[[!commit 6fb43c29f63b85c3424520819427903e5a204426]] is relevant to that,
and I guess it didn't fully solve the problem.
--[[Joey]]
