Summary:
This is copied from the Sharness repository’s `test/.gitignore`, and is
also the same as Git’s `t/.gitignore` minus a Git-specific exclusion.
Suggested by @decentralion.
Test Plan:
Run `yarn sharness` and interrupt it (SIGINT) while `make` is running.
Note that `sharness/` now contains a `trash directory.*`, which Git
ignores.
wchargin-branch: sharness-gitignore
William Chargin