· If the pattern does not contain a slash /, git treats it as a shell
glob pattern and checks for a match against the pathname relative
to the location of the .gitignore file (relative to the toplevel of
the work tree if not from a .gitignore file).
· Otherwise, git treats the pattern as a shell glob suitable for
consumption by fnmatch(3) with the FNM_PATHNAME flag: wildcards in
the pattern will not match a / in the pathname. For example,
"Documentation/*.html" matches "Documentation/git.html" but not
"Documentation/ppc/ppc.html" or
"tools/perf/Documentation/perf.html".