feat(#1837): add git.disable_for_dirs

[alex-courtis]

fixes #1837

@NiklasKappel I'd be most grateful if you tested this feature:

cd /path/to/nvim-tree.lua
git pull
git checkout 1837-git-disable-dirs

[NiklasKappel]

@NiklasKappel I'd be most grateful if you tested this feature:

Both disabled_dirs = { "~/" } and disabled_dirs = { "/var/home/niklas/" } work for me to disable git integration for my home directory (I can no longer see the the icons in nvim-tree that indicate changed or new files).

Interestingly, I can not reproduce the delay I originally described in #1837 right now, neither with the master branch nor this branch. Was there a change to how nvim-tree treats untracked files in the meantime?

[alex-courtis]

Interestingly, I can not reproduce the delay I originally described in #1837 right now, neither with the master branch nor this branch. Was there a change to how nvim-tree treats untracked files in the meantime?

Background git operation experiment was recently concluded and always enabled #2104
That may be the reason for the increase in speed.

Thank you for testing this out.