Re: On git 1.6 (novice's opinion)

From: Ulrich Windl <ulrich.windl@rz.uni-regensburg.de>
Date: Apr 1, 2009, 09:38 UTC
Message-ID: <49D35254.4137.CB56FE@Ulrich.Windl.rkdvmks1.ngate.uni-regensburg.de>
In-Reply-To: <vpq63horepl.fsf@bauges.imag.fr>

On 1 Apr 2009 at 9:54, Matthieu Moy wrote:

Show 19 quoted lines

> "Ulrich Windl" <ulrich.windl@rz.uni-regensburg.de> writes:
> 
> >> Not to mention that you can have multiple roots (multiple commits with
> >> no parent) in git repository; besides independent branches (like
> >> 'man', 'html' or 'todo') it is usually result of absorbing or
> >> subtree-merging other projects.  In 'master' branch there are 5 roots
> >> or more: joined 'git-tools' (mailinfo / mailsplit), absorbed gitweb,
> >> and subtree-merged gitk and git-gui.  And here you would again have
> >> multiple commits with the same number...
> >
> > Which would not harm, because it would be version N from committer X. Any if 
> > committer X merges from anything else, the next number would be > N. I did not 
> > claim that my method makes a total ordering of commits and merges possible.
> 
> Neither does it make the numbers unique for committer X.
> 
> If commiter X commits a successor to commit N, it's labeled N+1. If
> later, he creates another branch from commit N, and commit, the new,
> other commit will be labeled N+1.

Correct: They live in a parallel universe. But on the long term they will either 
vanish or be merged in which case the number will be "> N+1" (on the main branch). 
So we have a branch plus a sequence number all the time.

> 
> This means even within a repository, you cannot say things like
> "commit number N", so, OK, you have numerical IDs, but you can't use
> them.

I never wanted to have such a thing (using those numbers for commit).

Show 5 quoted lines

> 
> What can be interesting is that a commit takes 
> max{all commits in repository}+1, not just max{parents} + 1. Then, you
> have local revision numbers, but they're not stable. Indeed, that's
> precisely what Mercurial does.

That would be a (temporary) total ordering, which I did not want, exactly for that reason.

[I did not intend the following use case]

Ulrich

Show 21 quoted lines

> 
> But I'm not sure how much simplicity it adds compared to the confusion
> it adds. Newbies will see Mercurial identifiers as
> 
> changeset:   2:699b81a5851b
> changeset:   1:fd4b6597548f
> changeset:   0:58cff172192e
> 
> And think "OK, the revision numbers are 0, 1, 2, and the hexadecimal
> stuff beside is useless". And one day, he'll send a mail, post a
> bugreport, or whatever, saying "I have a problem with revision number
> 42", and no one else but him will know which revision is called "42".
> 
> > I truly believe in unique IDs, but they are just not handy in every situation.
> 
> Usually, people find Git IDs to be non-handy until the find out they
> can cut-and-paste only the first few digits in most cases, like
> 442dd42 instead of 442dd42d6d4903640b0dc5561481a77c88dcea90 ;-).
> 
> -- 
> Matthieu