Re: [PATCH] commit: Add -f, --fixes <commit> option to add Fixes: line

>
> Thinking aloud further, what I had in mind was along the lines of
> the following.
>
>  * The most generic external interface would be spelled as
>
>     --trailer <token>[=<param>]
>
>    where <token> can be things like "signoff", "closes", "acked-by",
>    "change-id", "fixes", etc.; they can be taken from an unbounded
>    set.  The historical "--signoff" can become a short-hand for
>    "--trailer signoff".  More than one "--trailer" option can be
>    given on a single command line.

>  * The token is used to look into the configuration, e.g.,
>
>    [commitTrailer "signoff"]
>         style = append-norepeat
>         trailer = Signed-off-by
>         command = echo "$GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>"'
>
>    [commitTrailer "change-id"]
>         style = append-only-if-missing
>         trailer = Change-Id
>         command = 'git hash-object -t commit --stdin <$GIT_PROTO_COMMIT'
>
>    [commitTrailer "fixes"]
>         style = overwrite
>         trailer = Fixes
>         command = 'git log -1 --oneline --format="%h (%s)" --abbrev-commit=14 $ARG'
>
>    where
>
>    - "commitTrailer.<token>.style" defines the interaction with
>      existing trailer of the same kind (e.g. S-o-b: accumulates by
>      appending, but we try not to repeat the same sign-off twice
>      which would show you forwarding your own message you are the
>      last person in the Sign-off chain; Fixes: if there is already
>      one will remove the old one and replaces; etc.);
>
>    - "commitTrailer.<token>.trailer" defines the trailer label at
>      the beginning of the trailer line;
>
>    - "commitTrailer.<token>.command" gives the command to run to
>      obtain the payload after the "trailer" label.  A handful
>      obvious and useful variables are exported for the command to
>      use, and <param> is exported as $ARG, if present.
>
> With the most generic syntax, with the above commitTrailer.fixes.*
> configuration, I would imagine that you can say something like:
>
>     git commit --trailer fixes="v2.6.12^{/^i386: tweak frobnitz}"
>
> to say that the first commit you find traversing the history of
> v2.6.12 whose title is "i386: tweak frobnitz" was faulty, and you
> are creating a commit that corrects its mistake.
>
> Giving some default configuration to often used trailer types
> (e.g. configuration for "--trailer signoff") and promoting some
> commonly used ones into a separate built-in option (e.g. an option
> "--signoff" that does not have to say "--trailer signoff") are
> entirely separate issues, and only time can nudge us into evaluating
> individual types of trailers.