Watcher wants to rewrite symlink to fix it. But in direct mode, the symlink
could be replaced at any time with file content that has finished being
transferred by some other process. So, just don't touch it.
FWIW, I audited the rest of the assistant for places where it removes
files, and the rest is ok. I have not audited the rest of git-annex.
assistant: Fix bug in direct mode that could occur when a symlink is moved
out of an archive directory, and resulted in the file not being set to
direct mode when it was transferred.
The bug was that the direct mode mapping was not up-to-date when the
transferrer finished. So, finding no direct mode place to store the object,
it was put into .git/annex in indirect mode.
To fix this, just make the watcher update the direct mode mapping to
include the new file before it starts the transfer. (Seems we don't need to
update it to remove the old file if the link was moved, because the direct
mode code will notice it's not present and the mapping gets updated for its
removal later.)
The reason this was a race, and was probably not seen often is because
the committer came along and updated the direct mode mapping as part of
adding the moved symlink. But when the file was sufficiently small or
the remote sufficiently fast, this could happen after the transfer
finished.
Looking through the git sources (documentation is unclear),
it seems commit doesn't ever trigger git-gc, mostly fetching and merging
seems to. I cannot easily override the setting in all those places, so
instead set gc.auto in git config when initializing a repository with
the assistant.
This does mean that the user cannot set gc.auto=0 and completely avoid
repacks, as the assistant does it daily. But, it only does it after there
are 100x the default number of loose objects, so this is probably not going
to be too annoying.
