Re: [PATCH 2/2] merge: make sure to terminate message with newline

[Jeff King <peff@peff.net>]

On Fri, Jul 16, 2021 at 01:34:58PM -0700, Junio C Hamano wrote:

> Jeff King <peff@peff.net> writes:
> 
> > I think we still end up calling cleanup_message() on the result before
> > using it as the final message, and that will fix any missing newline.
> > But we feed the intermediate state before then to the hooks (which is
> > exactly where one might expect to use interpret-trailers).
> >
> > I'm not sure if we should be doing a preemptive call to
> > cleanup_message() before feeding the hooks (we'd still need to do the
> > final one, to clean up whatever the hooks return to us). I guess
> > probably not, because I think that would remove comments, as well. So
> > adding in just the missing newline is probably better.
> 
> To be quite honest, I think this patch is a half-way solution and I
> am not sure if it is better than either of the two "purist"
> extremes:
> 
>  * If the hooks want to see messages with as little loss of
>    information from the original as possible, we should give them
>    without clean-up (which you pointed out above) *and* without this
>    patch.
> 
>  * If the hooks want to see messages as canonicalized as people
>    would see in normal "git log" output, we should be passing the
>    full clean-up to lose even comments and in such a case there is
>    no need for this "always terminate" patch (we'd instead do far
>    more).
> 
> Between the two approaches, both are purists' view, I'd prefer the
> former, but from that stance, the conclusion would become that there
> is no need to do anything, which may be a bit unsatisfactory.

Yes, I agree with all of that (including the "as little loss of
information as possible" preference).

> > Since it will usually be added back in by cleanup_message() anyway, I
> > think it's OK to just add it preemptively. The exception would be if the
> > user asked for no cleanup at all. So making it conditional on
> > cleanup_mode would work, whether -F or not.
> >
> > I suppose that does mean people turning off cleanup mode would get a
> > message without a newline from fmt_merge_msg(), though, which is perhaps
> > unexpected.
> >
> > So maybe just keeping the newline there, as you suggest, is the best
> > way.
> 
> Hmph.
> 
> If the user tells us "refrain from touching my message as much as
> possible" and feeds us a proposed log message that ends with an
> incomplete line, I would think they expect us not to turn it into a
> complete line, and I would think doing this change only when cleanup
> is in effect would make sense.  This is especially true for users
> who do not let any hooks to interfere.  They used to get their
> incomplete lines intact, now their incomplete lines will
> unconditionally get completed.  I am not sure if I would want to
> defend this change from their complaints.

Right, what I was suggesting was:

  if (cleanup_mode != COMMIT_MSG_CLEANUP_NONE)
	strbuf_complete(&msg);

which would cover that case. But Phillip mentioned that our own
fmt_merge_msg() does not include a newline. So it would not be the user
feeding us an incomplete line, but rather Git feeding it. And that was
what I suggested should be corrected (which I suppose would be in
addition to correcting lines from the user).

However, I see a call to strbuf_complete_line() at the end of
fmt_merge_msg(), so I am puzzled about what he meant.

-Peff