If an input file has been lost from all repositories, it is no longer
possible to compute the output. This will avoid dropping content that
was computed in such a situation, as well as making git-annex fsck --from
the compute remote do its usual thing when content has gone missing.
This implementation avoids recursing forever if there is a cycle,
which should not be possible anyway.
Note the use of RemoteStateHandle as a constructor here suggests that
this may not handle sameas remotes right, since usually a
RemoteStateHandle is constructed using the sameas uuid for a sameas
remote. That assumes a compute remote can even have or be a sameas remote.
Which doesn't seem to make sense, so I have not thought through what might
happen here in detail.
If it did, recompute would need to somehow support recomputing
non-annexed files.
And, annex.smallfiles is typically used for configuration files or
source code kind of things, where the user doesn't want it to be an
annexed file. Computed artifacts are not likely that kind of thing.
Also, git-annex importfeed is an example of something that does support
annex.addunlocked, but does not support annex.smallfiles.
When writing doc/tips/computing_annexed_files.mdwn, I noticed
that a recompute --reproducible followed by a drop and a re-get did not
actually test if the file could be reproducible computed again.
Turns out that get and drop both operate on staged files. If there is an
unstaged modification in the work tree, that's ignored. Somewhat
surprisingly, other commands like info do operate on staged files. So
behavior is inconsistent, and fairly surprising really, when there are
unstaged modifications to files.
Probably this is rarely noticed because `git-annex add` is used to add a
new version of a file, and then it's staged. Or `git mv` is used to move
a file, rather than `mv` of a file over top of an existing file. So it's
uncommon to have an unstaged annexed file in a worktree.
It might be worth making things more consistent, but that's out of scope
for what I'm working on currently.
Also, I anticipate that supporting unlocked files with recompute will
require it to stage changes anyway.
So, make recompute stage the new version of the file.
I considered having recompute refuse to overwrite an existing staged
file. After all, whatever version was staged before will get lost when
the new version is staged over top of it. But, that's no different than
`git-annex addcomputed` being run with the name of an existing staged
file. Or `git-annex add` being run with a new file content when there is
an existing staged file. Or, for that matter, `git add` being ran with a
new content when there is an existing staged file.
This avoids a potential problem where the program sends several INPUT
before reading responses, so flushing the respose to the pipe could
block. It's unlikely, but seemed worth making sure it can't happen.
Used by git-annex-compute-singularity to make addcomputed --fast work.
Also, simplified git-annex-compute-singularity; there is no need to hard
link the container into place. singularity does not care about the
extension of the container, so can just pass it the annex object file.
