ab/parse-options-cleanup & ab/align-parse-options-help & ab/help-config-vars

> * ab/parse-options-cleanup (2021-10-01) 11 commits
>  - 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_type"
>  - 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
>
>  Random changes to parse-options implementation.
>
>  Will merge to 'next'?

> * ab/align-parse-options-help (2021-09-22) 4 commits
>  - parse-options: properly align continued usage output
>  - git rev-parse --parseopt tests: add more usagestr tests
>  - send-pack: properly use parse_options() API for usage string
>  - parse-options API users: align usage output in C-strings
>
>  When "git cmd -h" shows more than one line of usage text (e.g.
>  the cmd subcommand may take sub-sub-command), parse-options API
>  learned to align these lines, even across i18n/l10n.
>
>  Will merge to 'next'?

> * ab/help-config-vars (2021-09-23) 9 commits
>  - help: move column config discovery to help.c library
>  - help / completion: make "git help" do the hard work
>  - help tests: test --config-for-completion option & output
>  - help: simplify by moving to OPT_CMDMODE()
>  - help: correct logic error in combining --all and --guides
>  - help: correct logic error in combining --all and --config
>  - help tests: add test for --config output
>  - help: correct usage & behavior of "git help --guides"
>  - help: correct the usage string in -h and documentation
>
>  Teach "git help -c" into helping the command line completion of
>  configuration variables.
>
>  Will merge to 'next'?