feat(cli): Add --working-directory option

[arxanas]

No description provided.

[epage]

Could you help me understand the motivation? I'm not seeing git implement this, so its not for parity.

[arxanas]

Oops, the motivation was in the commit message:

This is useful for an invocation of cargo flamegraph (and also probably for cargo run):

cargo flamegraph --bin git-stack --root -- --working-directory <repo>

The corresponding option in Git is -C.

[epage]

Oh, thanks!

I'll look at this more on monday to decide what the semantics should be standalone and as a git subcommand.

Right now I'm leaning towards this being -C and matching git's semantics (allowing multiple and doing path joins on them) but having it hidden as people will most likely be using it via git. I also want to see how git passes state for other related path flags to subcommands, like --git-dir, to make sure we respect them as well.

[arxanas]

I suppose that if users can use -C from Git itself, then it might be better to hide this option and/or rename it so that it's obvious that it's for testing, or use a different mechanism like environment variables, or just drop the feature altogether since its use is limited. (For git-branchless, I added a -C flag primarily for testing with cargo run, but it doesn't actually do the behavior when specifying the flag multiple times.)

[epage]

Closing in favor of #197