Re: Referring to revisions in the git future.

[Alan Mackenzie]

Hello, David.

On Sat, Nov 01, 2014 at 11:29:47AM +0100, David Kastrup wrote:
> Alan Mackenzie <address@hidden> writes:

> > On Sat, Nov 01, 2014 at 08:49:34AM +0100, David Kastrup wrote:
> >> It's not like anybody's going to want to type off "abbreviations" by
> >> hand anyway: too error-prone.

> > I'm going to want to do this, that's why I started this thread.  Using a
> > computer to kill and yank such a number is going to be such a downer.  Do
> > you also kill and yank a variable name each time you need to type it in,
> > or do you just type it?

> > Likely, I'm not going to be able to do this.  Remembering and typing in a
> > revision number is trivial: two chunks of memory - one for the bit that
> > slowly changes "118" the other for the "220" at the end.  With 40 digit
> > hex strings, even abbreviated, it's going to be 6 or 7 chunks to
> > memorise.  As you say, this will be error-prone.

> >> Just paste the full thing.  Really.  I've been developing for years
> >> with Git, and that's just what everybody does most of the time.

> > Because they have to, not because it's their preferred way of working.

> Do you really think you know me better than I do?

No, I don't, thankfully.  Just as you don't know what "anybody"'s going
to want to do, better than the anybody himself does.

> If you do, you can just continue this discussion in your imagination and
> not bother the list with it.  I've worked with sequential numbers for
> decades.  Everybody did in the time of RCS and CVS.  I've worked with
> Git and SHA-1 for quite some time, too.

I've been working with bzr, which uses hashes, for some while.  Funnily
enough, I can't remember anybody on emacs-devel referring to a revision
by that hash (except in discussions such as this one).  The revision
number has been used many, many times.

> You didn't apparently.  And yet you think yourself more qualified than I
> am to tell people about _my_ motivations?

Calm down, David!  Feel free to insert a "necessarily" into the last
sentence of my previous post.  It would clarify my meaning.

> SHA1 is _great_ for mailing lists, by the way.  You plug in an SHA1 into
> a mailing list search, and out fall all relevant mails.

OK, I'll believe you.  That's assuming you type in a short enough
abbreviation, or the person writing the email has typed in the full hash.
Presumblay people using git do type in the full hash.  You wouldn't get
very far with that strategy on emacs-devel, though, at least not as yet.

Incidentally there have been five threads on emacs-devel which have
referred to version numbers 118xxx.  Clearly a lot of people find these
numbers convenient and useful.

> Try that with a sequence number.

Just done it (see above) with a regexp search.  It worked well, although
there were lots of false matches, of course.  The only regexp searches
you can do for hashes are for messages which include one at all, or for
single specific hashes.  If you know roughly a specific revision lies
between 33b57e7 and 16181a4, you've no way of searching an email list
for mentions of it.  On the other hand, if it's between 118204 and
118499, you'll find it easily.

> You plug in an SHA1 of some commit with inscrutable commit message
> missing an issue number into an issue tracker, and out falls the
> message reporting the closing of the issue with a particular commit.
> It's a real life-saver for finding stuff again.  Neither abbreviated
> SHA1 nor sequence numbers work for that.

Yes, that sounds like an excellent reason for using hashes.  But for many
uses, a revision number is better.  bzr has them both.  git doesn't.

> -- 
> David Kastrup

-- 
Alan Mackenzie (Nuremberg, Germany).