Johan Herland [off-list ref] writes:
While pushing to a remote repo, Git transiently adds a .keep file for the
pack being pushed, to protect it from a concurrent "git gc". However, the
permissions on this .keep file are such that if a different user attempts
a local cross-filesystem clone ("git clone --no-hardlinks") on the server
while the .keep file is present (either because of a concurrent push, or
because of a prior failed push that left a stale .keep file), the clone
will fail because the second user cannot access the .keep file created by
the first user.
While I am not sure if letting a clone proceed while there is a concurrent
push is even a good idea to begin with, I agree that a stale .keep file is
a problem.
I am kind of surprised that we are not using atexit(3) to clean them just
like we do for lockfiles; wouldn't that be a better solution?