Check Ignore Rules

When a file unexpectedly does (or does not) show up in git status, it can be hard to tell which rule is responsible. Git provides a tool just for this:

git check-ignore -v build/output.txt

If the file matches an ignore rule, Git prints which file and which line caused the match:

.gitignore:1:build/    build/output.txt

If you want a yes/no answer for one path, omit the -v flag. Git exits with status 0 if the file is ignored and 1 if it is not, and prints the path only when matched.

For a quick listing of "all matched files", you can use:

git check-ignore *

This is invaluable for debugging tricky .gitignore configurations on real projects.