Merge branch 'jk/shorten-unambiguous-ref-wo-sscanf'

sscanf(3) used in "git symbolic-ref --short" implementation found to be not working reliably on macOS in UTF-8 locales. Rewrite the code to avoid sscanf() altogether to work it around. * jk/shorten-unambiguous-ref-wo-sscanf: shorten_unambiguous_ref(): avoid sscanf() shorten_unambiguous_ref(): use NUM_REV_PARSE_RULES constant shorten_unambiguous_ref(): avoid integer truncation