Re: [PATCH 0/2] git-am: add --message-id/--no-message-id options

[Christian Couder <christian.couder@gmail.com>]

On Tue, Nov 25, 2014 at 6:01 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
>
> On 25/11/2014 17:27, Christian Couder wrote:
>>> > From: Paolo Bonzini <pbonzini@redhat.com>
>>> >
>>> > This series adds a --message-id option to git-mailinfo and git-am.
>>> > git-am also gets an am.messageid configuration key to set the default,
>>> > and a --no-message-id option to override the configuration key.
>>> > (I'm not sure of the usefulness of a mailinfo.messageid option, so
>>> > I left it out; this follows the example of -k instead of --scissors).
>>> >
>>> > This option can be useful in order to associate commit messages with
>>> > mailing list discussions.
>>> >
>>> > If both --message-id and -s are specified, the Signed-off-by goes
>>> > last.  This is coming out more or less naturally out of the git-am
>>> > implementation, but is also tested in t4150-am.sh.
>> Did you have a look at git interpret-trailers currently in master?
>
> Hmm, now I have.
>
> As far as I understand, all the git-am hooks are called on the commit
> rather than the incoming email: all headers are lost by the time
> git-mailinfo exits, including the Message-Id.  And you cannot call any
> hook before git-mailinfo because git-mailinfo is where the
> Content-Transfer-Encoding is processed.
>
> How would you integrate git-interpret-trailers in git-mailinfo?

I don't know exactly, but people may want to add trailers when they
run git-am, see:

http://thread.gmane.org/gmane.comp.version-control.git/251412/

and we decided that it was better to let something like git
interpret-trailers decide how they should be handled.

Maybe if git-interpret-trailers could be called from git-mailinfo with
some arguments coming from git-am, it could be configured with
something like:

git config trailer.Message-Id.command 'perl -ne '\''print $1 if
m/^Message-Id: (.*)$/'\'' $ARG'

So "git am --trailer 'Message-Id: msg-file' msg-file" would call "git
mailinfo ..." that would call "git interpret-trailers --trailer
'Message-Id: msg-file'" that would call "perl -ne 'print $1 if
m/^Message-Id: (.*)$/' msg-file" and the output of this command, let's
call it $id, would be put into a "Message-Id: $id" trailer in the
commit message.

This way there is nothing specific to Message-Id in the code and
people can decide using other trailer.Message-Id.* config variables
exactly where the Message-Id trailer would be in the commit message.

Best,
Christian.