Using GIT keys, like are used when exporting git files to special
remotes. Except here the GIT key refers to a file checked into the git
repo.
Note that, since the compute remote uses catObject to get the content,
a symlink that is checked into git does not get followed. This is important
for security, because following a symlink and adding the content to the
repo as an annex object would allow exfiltrating content from outside
the repository.
Instead, the behavior with a symlink is to run the computation on the
symlink target. This may turn out to be confusing, and it might be worth
addcomputed checking if the file in git is a symlink and erroring out.
Or it could follow symlinks as long as the destination is a file in the
repisitory.
I've lost track of them all, but it includes:
* Using the same key backend as was used in the original computation.
* Fixing bug that prevented updating the source file key in the compute
state
* Handling --reproducible and --unreproducible.
* recompute --original of a file using VURL, when the result is
different, but the key remains the same, makes the object file
be updated with the new content
* Detecting some other ways the program behavior can change, just for
completeness.
* Also adds --backend to addcomputed.
The perform action of this still needs work to do the right thing.
In particular, it currently behaves as if --others was always set.
And, it duplicates a lot of code from addcomputed.
This is limited because the remote config is a field/value map. So order
is not preserved, and when 2 parameters have the same field name, only
the last one will be passed.
For these, use VURL and URL keys, with an "annex-compute:" URI prefix.
These URL keys will look something like this:
URL--annex-compute&cbar4,63pconvert,3-f4d3d72cf3f16ac9c3e9a8012bde4462
Generally it's too long so most of it gets md5summed. It's a little
ugly, but it's what fell out of the existing URL key generation
machinery. I did consider special casing to eg
"URL--annex-compute&c4d3d72cf3f16ac9c3e9a8012bde4462". But it seems at
least possibly useful that the name of the file that was computed is
visible and perhaps one or two words of the git-annex compute command
parameters.
Note that two different output files from the same computation will get
the same URL key. And these keys should remain stable.
Eg, a computation might be run in "foo/" and refer to "../bar" as an
input or output.
So, the subdir is part of the computation state.
Also, prevent input or output of files that are outside the git
repository. Of course, the program can access any file on disk if it
wants to; this is just a guard against mistakes. And it may also be
useful if the program comunicates with something less trusted than it,
eg a container image, so input/output files communicated by that are not
the source of security problems.
