A gitignore pattern with no slash matches at every depth, so it can swallow a source directory

Fact

A .gitignore pattern that contains no slash other than a trailing one matches anywhere in the tree, not just at the repository root. target/ — copied into almost every JVM project's ignore file for Maven's output — also ignores src/main/java/com/example/target/, and build/, bin/ and out/ behave the same way.

Why it matters

git add reports nothing, git commit succeeds, and the push goes out with a whole package missing. The local build keeps passing because the files are still on disk; the first symptom is CI failing to compile, or a fresh clone missing code that "is definitely committed".

How to apply

• Anchor build-output patterns to the root with a leading slash: /build/, /target/, /out/, /bin/.
• Before the first push of a new repository, read the staged list rather than trusting the command: git status --short or git diff --cached --name-only. A commit hash proves a commit happened, not that it contains what you think.
• git check-ignore -v <path> names the pattern and the file it came from when something is missing.