GitProcessor: run `git branch` from a specified directory instead of working directory

[root-talis]

When running a script from cron it is very possible that the working directory will not match the script directory. In this case, instead of logging the git version, GitProcessor logs this:

fatal: not a git repository (or any of the parent directories): .git
[2021-03-10 10:26:46] channel.LEVEL: Something happened [] {"git":[]}

This happens every time something is logged. Not only this is unhelpful, but it is also annoying because analyzing such logs becomes an issue: fatal is a keyword by which one might want to filter their logs.

It would be nice to make it possible to specify the directory in which git branch should be run, for example via a configuration value passed to the constructor.

[Seldaek]

I guess as a workaround you could make sure to call $gitProcessor([]) early in your process before you change the directory, to make sure the cache is populated.

But otherwise if you like to send a PR adding a new $path option, that sounds good to me.