Merge branch 'cc/skip-to-optional-val'

Introduce a helper to simplify code to parse a common pattern that expects either "--key" or "--key=<something>". * cc/skip-to-optional-val: t4045: reindent to make helpers readable diff: add tests for --relative without optional prefix value diff: use skip_to_optional_arg_default() in parsing --relative diff: use skip_to_optional_arg_default() diff: use skip_to_optional_arg() index-pack: use skip_to_optional_arg() git-compat-util: introduce skip_to_optional_arg()