Is there a way to use extended regular expressions(ERE) in a .gitignore file? For example I want to use the + repetition character in a .gitignore file. Is there a way to do that?
As illustrated here and detailed in "this question", the function fnmatch() is involved to interpret glob patterns, which means regular expressions are not supported.
This is what gitignore man page mentions:
Otherwise,
git treats the pattern as a shell glob suitable for consumption by fnmatch(3)with theFNM_PATHNAMEflag: 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".
You can see some correspondence between glob patterns and regular expressions in those questions.