Coqdeplib.File_utilto_relative_path path takes as input a file path path, and constructs an equivalent relative path from the current working directory. If path is already relative, then it is returned immediately.
normalize_path path takes as input a file path path, and returns an equivalent path that: (1) does not contain the current directory member "." unless the path is to the current directory (in which case "." is returned, or "./" if path has a trailing "/"), (2) only uses parent directory members ".." for a prefix of the path, and (3), has a trailing "/" only if and only if path does.
For example, paths "dir1/dir2/file.v", ".", "dir1/dir2/dir3/" and "../../dir/file.v" are possible return values, but "./file.v" and "dir1/../dir2" are not.