* ps/stash-in-c: (28 commits)
tests: add a special setup where stash.useBuiltin is off
stash: optionally use the scripted version again
stash: add back the original, scripted `git stash`
stash: convert `stash--helper.c` into `stash.c`
stash: replace all `write-tree` child processes with API calls
stash: optimize `get_untracked_files()` and `check_changes()`
stash: convert save to builtin
stash: make push -q quiet
stash: convert push to builtin
stash: convert create to builtin
stash: convert store to builtin
stash: convert show to builtin
stash: convert list to builtin
stash: convert pop to builtin
stash: convert branch to builtin
stash: convert drop and clear to builtin
stash: convert apply to builtin
stash: mention options in `show` synopsis
stash: add tests for `git stash show` config
stash: rename test cases to be more descriptive
...