fix(vcs): remove empty paths from repo.get_tracked_files()

[ahal]

The test should be exercising this code path, so I'm not really sure why it passes in Taskgraph but failed in another case in CI. Maybe it's related to the version of Git on the worker.

[jcristau]

I don't understand why this would make a difference?

[bhearsum]

I don't understand why this would make a difference?

Git (at least some versions of it?) seem to not like the empty argument:

~/repos/translations gpu-multi:main ⇡9 *75 ❯ git ls-tree -r --name-only HEAD '' | wc -l        
fatal: empty string is not a valid pathspec. please use . instead if you meant to match all paths
0
~/repos/translations gpu-multi:main ⇡9 *75 ❯ echo $?                             
0
~/repos/translations gpu-multi:main ⇡9 *75 ❯ git ls-tree -r --name-only HEAD | wc -l   
695

[jcristau]

That part I can understand, but I don't see how this patch changes that.

[hneiva]

To Julien's point, this isn't removing any empty strings:

>>> a = []
>>> [1,2,3,*a]
[1, 2, 3]

>>> a = ['']
>>> [1,2,3,*a]
[1, 2, 3, '']

If the idea is to filter out, you'd probably need something like [p for p in paths if p]

[jcristau]

Indeed. (Also, it'd be good to understand/document why/how an empty string would come in here, naively that seems like it'd be a bug elsewhere.)

[ahal]

Ah thanks, that makes more sense. Looks like the empty string is ultimately coming from graph_config.vcs_root which I assumed would be absolute, but I guess it's relative.

[ahal]

I decided to strip out empty strings rather than make graph_config.vcs_path absolute to avoid causing issues elsewhere.

[jcristau]

I'm not sure I like the semantics here (vs fixing the caller to not pass the empty string) but it's probably fine.

[bhearsum]

While looking at possibly changing the callers as @jcristau suggested I stumbled upon the fact that vcs_root ends up being an empty string most of the time due to #673. That may negate the need for this patch, although this (or something similar) is probably a fix that we want even if there's no current bustage.