In a situation where there are two repos that are diverged and each pushes
in turn to git-remote-annex, the first to push updates it. Then the second
push fails because it is not a fast-forward. The problem is, before git
push fails with "non-fast-forward", it actually calls git-remote-annex
with push.
So, to the user it appears as if the push failed, but it actually reached
the remote, and overwrote the other push!
The only solution to this seems to be for git-remote-annex push to notice
when a non-force-push would overwrite a ref stored in the remote, and
refuse to push that ref, returning an error to git. This seems strange,
why would git make remote helpers implement that when it later checks the
same thing itself?
With this fix, it's still possible for a race to overwrite a change to
the MANIFEST and lose work that was pushed from the other repo. But that
needs two pushes to be running at the same time. From the user's
perspective, that situation is the same as if one repo pushed new work,
then the other repo did a git push --force, overwriting the first repo's
push. In the first repo, another push will then fail as a non
fast-forward, and the user can recover as usual. But, a MANIFEST
overwrite will leave bundle files in the remote that are not listed in
the MANIFEST. It seems likely that git-annex will eventually be able to
detect that after the fact and clean it up. Eg, it can learn all bundles
that are stored in the remote using the location log, and compare them
to the MANIFEST to find bundles that got lost.
The race can also appear to the user as if they pushed a ref, but then
it got deleted from the remote. This happens when two two pushes are
pushing different ref names. This might be harder for the user to
notice; git fetch does not indicate that a remote ref got deleted.
They would have to use git fetch --prune to notice the deletion.
Once the user does notice, they can re-push their ref to recover.
Sponsored-by: Jack Hill on Patreon
This is a shell script, so not final code, and it does not use git-annex
at all, but it shows how to push to git bundles, listed in a MANIFEST,
the same as the git-remote-annex program will eventually do.
While developing this, I realized that the design needed to be changed
slightly regarding where refs are stored. Since a push can delete a ref
from a remote, storing each newly pushed ref in a bundle won't work,
because deleting a ref would then entail deleting all old bundles and
re-uploading from scratch. So instead, only the refs in the last bundle
listed in the MANIFEST are the active refs. Any refs in prior bundles
are just old refs that were stored previously (a reflog as it were).
That means that, in a situation where two different people are pushing
to the same special remote from different repos, whoever pushes last
wins. Any refs pushed by the other person earlier will be ignored. This
may not be desirable, and git-annex might be able use the git-annex
branch to detect such situations and rescue the refs that got lost. Even
without such a recovery process though, the refs that the other person
thought they pushed will be preserved in their refs/namespaces/mine, so
a pull followed by a push will generally resolve the situation.
Note that the use of refs/namespaces/mine in the bundle is not really
desirable, and it might be worth making a local clone of the repo in
order to set up the refs that will be put in the bundle. Which seems to
be the only way to avoid needing that. But it does need to maintain
the refs/namespaces/mine/ in the git repo in order to remember what refs
have been pushed to the remote before, in order to include them in the
next bundle pushed. A name that includes the remote uuid will be needed
in the final implementation.
Anyway, this shell script seems to fully work, including incremental
pushing, force pushing, and pushes that delete refs.
Sponsored-by: Brett Eisenberg on Patreon
Improve handling of some .git/annex/ subdirectories being on other
filesystems, in the bittorrent special remote, and youtube-dl integration,
and git-annex addurl.
The only one of these that I've confirmed to be a problem is in the
bittorrent special remote when .git/annex/tmp and .git/annex/othertmp are
on different filesystems.
As well as auditing for renameFile, also audited for createLink, all of
those are ok as are the other remaining renameFile calls. Also audited all
code paths that use .git/annex/othertmp, and did not find any other
cross-device problems. So, removing mention of othertmp needing to be on
the same device.
Sponsored-by: Dartmouth College's Datalad project
This format is designed to detect accidental appends, while having some
room for future expansion.
Detect when an unlocked file whose content is not present has gotten some
other content appended to it, and avoid treating it as a pointer file, so
that appended content will not be checked into git, but will be annexed
like any other file.
Dropped the max size of a pointer file down to 32kb, it was around 80 kb,
but without any good reason and certianly there are no valid pointer files
anywhere that are larger than 8kb, because it's just been specified what it
means for a pointer file with additional data even looks like.
I assume 32kb will be good enough for anyone. ;-) Really though, it needs
to be some smallish number, because that much of a file in git gets read
into memory when eg, catting pointer files. And since we have no use cases
for the extra lines of a pointer file yet, except possibly to add
some human-visible explanation that it is a git-annex pointer file, 32k
seems as reasonable an arbitrary number as anything. Increasing it would be
possible, eg to 64k, as long as users of such jumbo pointer files didn't
mind upgrading all their git-annex installations to one that supports the
new larger size.
Sponsored-by: Dartmouth College's Datalad project
Freeze first sets the file perms, and then runs
freezecontent-command. Thaw runs thawcontent-command before
restoring file permissions. This is in case the freeze command
prevents changing file perms, as eg setting a file immutable does.
Also, changing file perms tends to mess up previously set ACLs.
git-annex init's probe for crippled filesystem uses them, so if file perms
don't work, but freezecontent-command manages to prevent write to a file,
it won't treat the filesystem as crippled.
When the the filesystem has been probed as crippled, the hooks are not
used, because there seems to be no point then; git-annex won't be relying
on locking annex objects down. Also, this avoids them being run when the
file perms have not been changed, in case they somehow rely on
git-annex's setting of the file perms in order to work.
Sponsored-by: Dartmouth College's Datalad project
This avoids a proliferation of hash directories when using new-style
chunking, and should improve performance since chunks are accessed
in sequence and so should have a common locality.
Of course, when a chunked key is encrypted, its hash directories have no
relation to the parent key.
This commit was sponsored by Christian Kellermann.
Added new fields for chunk number, and chunk size. These will not appear
in normal keys ever, but will be used for chunked data stored on special
remotes.
This commit was sponsored by Jouni K Seppanen.
