faster-git.md

Steps to faster git on mac.

1. Update to git 2.16

2. Setup file monitoring with hgwatchman

   1. Run

   $ brew install watchman
   $ cd /path/to/mozilla-central
   $ watchman watch-project .
   

   2. Download my slightly modified version of the default git fsmonitor-watchman hook from here and put it at .git/hooks/fsmonitor-watchman.
   3. Run git config --local core.fsmonitor ".git/hooks/fsmonitor-watchman"

3. Enable git's split-index feature

   1. Run

   $ git update-index --split-index
   $ git config --system core.splitIndex true
   

   2. Optionally, run git config --local splitIndex.maxPercentChange 10. The default is 20, which is too high for repos the size of gecko. YMMV for a good value, you can also skip this and run git update-index --split-index whenever things start getting slow to force it to re-split the index.

4. Enable git's untracked file cache

   1. Run git update-index --test-untracked-cache. If it tells you you can, then
   2. Run git update-index --untracked-cache, and git config --system core.untrackedCache true.

5. If you still have a slow prompt, it's probably computing modifications in a bad way. Parsing them out of git status --porcelain is the fastest, but many use git diff --name-only or similar, which is very slow.