Currently we only read .lfsconfig from the working tree. This is better
than nothing, but it means that if there's an LFS file that starts with
a name earlier than .lfsconfig, we won't read the proper config file,
and we won't use any LFS remote URLs that are located in that file.
If the file is missing, let's additionally read from the index, if
there's a working tree, and then from HEAD. If the repository is bare,
let's just read from HEAD. This is very similar to what Git does for
.gitmodules.
It does, however, differ in one significant way: Git will read from the
index first if it's doing a checkout, since that might have newer
information. We don't do that here, since it's not totally clear that
we can articulate all the cases where that occurs in Git LFS, but we
explicitly allow for the possibility of changing the behavior in the
future and document the feature accordingly.
We no longer read the file .lfsconfig from a bare repository, but that
we did this in the first place was very questionable and pretty clearly
a bug, so it's intentional that we no longer do.
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