Re: Please don't use revision numbers on commit messages (and elsewhere).

[Stephen J. Turnbull]

Juanma Barranquero writes:
 > On Fri, Apr 1, 2011 at 02:11, Óscar Fuentes <address@hidden> wrote:
 > 
 > > The Emacs project has a number of branches published on a well-known
 > > site, and hopefully other branches distributed along a number of
 > > personal machines. I'm saying that using revision numbers is confusing
 > > when those revisions are merged across branches.
 > 
 > Yes, and I'm saying that, so far, it seems quite clear from the
 > context which branch a revno refers to.

That's only because so far, people don't lose push races often enough
for it to matter.  Commits that from your point of view are on the
mainline really are on local branches until you succeed in pushing.
If you use a bound branch, you're saved from that, true (this is not
entirely trivial, but I'm pretty sure in practice it will be true).
But bound branches suck for anything much bigger than a typo fix.

If you lose a push race, you have to undo the commit so you can redo
the commit message.  That (a) sucks even if you know what you're
doing, and (b) is probably beyond the average Emacs committer at that
moment.  (b) is no insult, just my estimate of a fact, and I see *no
reason* why that should change.  And of course (c) a lot of people
will forget (or never know about it in the first place).  I've been
annoyed by this a couple of times in XEmacs.

 > I don't foresee that super-distributed future that you imagine for
 > Emacs.

It doesn't require a super-distributed future, just an Emacs sprint.
Then you'll see people losing push races all over the place, and
anybody who's using revnos will have to go back and fix them.

 > And if it does come to pass, it's everyone's responsibility to
 > clearly label their revnos.

Well, OK, but I don't see how you can "label" a revno that's (a) just
plain wrong and (b) embedded in a commit message that can't be changed.

The right thing to do is to use a revid (which is bzr-friendly), or
ttn's literary style of commit message (which is people-friendly,
except to the committer and people who really exercise the capability
of the VCS).

 > No. Use always revision numbers and trust the users to be smart.

"Smart" is one thing, "anal retentive" is another.  Especially at any
time it's likely to matter (ie, the commit rushes that always occur
just before a freeze).  People are going to be frustrated enough by
losing push races.  They're not going to want to rebase their local
commits (and this has to be done by hand since the commit messages
need to be changed) at that point in time.