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

> * 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'?