commit: support granularity

[pared]

Update: see #4297 (comment)

version : 1.2.2

commiting output instead of stage, when there is no dvc.yaml results in:

ERROR: failed to commit data - 'dvc.yaml' does not exist.

in 0.94.0 it used to be:
ERROR: failed to commit data - bad DVC-file name 'data'. DVC-files should be named 'Dvcfile' or have a '.dvc' suffix (e.g. 'data.dvc').

Reproduction script:

#!/bin/bash

rm -rf repo
mkdir repo

pushd repo
git init --quiet
dvc init --quiet

echo data >> data
dvc add data

git add -A
git commit -am "init"

dvc commit data

NOTE:
When dvc.yaml is present, error is more readable:
failed to commit data - "Stage 'data' not found inside 'dvc.yaml' file"

[efiop]

The problem here is that we are using collect instead of collect_granular when resolving the target. Don't see us using it pre-1.0, so it is likely just a missing functionality. Likely just need to do the switch, but need to keep in mind that one might supply a file in a tracked directory, which needs to be handled appropriately (e.g. commiting the whole stage is probably not the desired behaviour). CC @skshetry or am I missing something and we've done that for a reason?

[skshetry]

@efiop, I don't think it was ever supported. Switching from collect to collect_granular would help, though it won't help with outputs being granular, it will commit all of the stage outputs.

[efiop]

@skshetry Thanks! So looks like collect_granular + filter_info support for commit and we should be set 🙂

[efiop]

Discussed with @skshetry that we could start with just output-level granularity, e.g.

dvc add datafile
...
dvc commit datafile

dvc add datadir
...
dvc commit datadir

More granular commits like

dvc add datadir
....
dvc commit datadir/subdir/file

would require a bit more work on cache.save side, for it to accept filter_info and handle it properly, so we could do it as the next step after output-level granularity.

[mbiesek]

@efiop I would like to start working on this.