Re: [BUG] git-am: all colons in the beginning of a subject are lost

[Jeff King <peff@peff.net>]

On Thu, Feb 28, 2019 at 11:02:11AM +0100, Max Filenko wrote:

>     Subject: [PATCH] :::: four colons prepended
> [...]
> There will be no colons in the beginning of a commit message if I apply
> this patch:
> 
>     $ git am 0001-four-colons-prepended.patch
>     Applying: four colons prepended

I suspect this has to do with the sanitization that happens as part of
removing "[PATCH]". Note that if you use "-k" (to preserve the subject)
it doesn't happen, though of course you also get "[PATCH]" then.

If you want to pass the subject lines through verbatim, use "-k" with
both format-patch and git-am.

> I was able to trace this down to <builtin/am.c>. It seems like there are
> no colons already in the `state->msg' which to my understanding is being
> filled by `read_commit_msg()' function. I would really appreciate a hand
> on debugging it further.

It's probably easier to debug with git-mailinfo, which has the same
behavior:

  $ git mailinfo msg patch <0001-four-colons-prepended.patch
  Author: Jeff King
  Email: peff@peff.net
  Subject: four colons prepended
  Date: Thu, 28 Feb 2019 06:12:50 -0500

and is based on the same routines.

The contents are preserved until we end up in mailinfo.c's
cleanup_subject(). And there leading colons are explicitly removed:

       case ' ': case '\t': case ':':
               strbuf_remove(subject, at, 1);
               continue;

That behavior goes all the way back to 2744b2344d (Start of early patch
applicator tools for git., 2005-04-11), when Git was only 4 days old.

Since it also handles cruft like "Re:", I suspect the goal there was I
suspect the goal there was to remove cruft like "Re::::" or "Re: :"
which sometimes happens. I don't know if anybody would complain if we
were more careful about leaving lone colons that weren't part of a "Re"
chain.

-Peff