and it will ignore all differences to other files.
The pattern is always the prefix, and is matched exactly. There are no
-wildcards. Even stricter, it has to match complete path comonent.
+wildcards. Even stricter, it has to match a complete path component.
I.e. "foo" does not pick up `foobar.h`. "foo" does match `foo/bar.h`
so it can be used to name subdirectories.