Merge branch 'ab/parse-options-cleanup'

Merge branch 'ab/parse-options-cleanup'

Random changes to parse-options implementation.

* ab/parse-options-cleanup:
  parse-options: change OPT_{SHORT,UNSET} to an enum
  parse-options tests: test optname() output
  parse-options.[ch]: make opt{bug,name}() "static"
  commit-graph: stop using optname()
  parse-options.c: move optname() earlier in the file
  parse-options.h: make the "flags" in "struct option" an enum
  parse-options.c: use exhaustive "case" arms for "enum parse_opt_result"
  parse-options.[ch]: consistently use "enum parse_opt_result"
  parse-options.[ch]: consistently use "enum parse_opt_flags"
  parse-options.h: move PARSE_OPT_SHELL_EVAL between enums