Bug: an invalid branch name does not produce a failure

[elliot-nelson]

SUMMARY

If I run pretty-quick with the --branch option and specify a branch that does not exist, I expect the tool to print out an appropriate error message and exit with exit code 1.

Instead, the tool "runs" without finding any issues:

❯ npx pretty-quick --branch asdf              
🔍  Finding changed files since git revision null.
🎯  Found 0 changed files.
✅  Everything is awesome!

This bug can cause lingering issues because a configuration problem (like passing in the wrong environment variable) can go a long time without being detected.