Re: Deciding between Git/Mercurial

["Björn Steinbrink" <B.Steinbrink@gmx.de>]

On 2009.09.29 20:49:52 -0400, Leo Razoumov wrote:
> On 2009-09-29, Jakub Narebski <jnareb@gmail.com> wrote:
> > On Tue, 29 Sep 2009, Leo Razoumov wrote:
> >  > On 2009-09-28, Jakub Narebski <jnareb@gmail.com> wrote:
> >  > > [..snip..]
> >  > >  Besides with nonlinear history with
> >  > >  revision numbers such as 12678 and 12687 you know that 12678 is older
> >  > >  than 12687 if and only if 12678 and 12687 are on the same line of
> >  > >  development.
> >  >
> >  > The statement above is incorrect!! In a Mercurial repo local revision
> >  > numbers are strictly ordered in commit time. 12678 < 12687 means that
> >  > 12678 was committed prior to 12687. But these two commits could belong
> >  > to two completely unrelated lines of development.
> >
> > This is impossible with distributed development.  If the second branch
> >  comes from other repository, with commits _created_ (in that repository)
> >  earlier than commits in current repository, but commits in first
> >  branch (from current repository) were created earlier than _fetching_
> >  those commits in second branch:
> >
> >   .---.---.---.---x---1---2---3---M---.
> >                    \             /
> >                     \-A---B---C-/             <-- from repository B
> >
> >
> >  Either you would have to change commits numbers, and therefore they would
> >  be not stable, or you would have to change commit time to mean 'time this
> >  commit got into current repository', which would kill performance for sure.
> >
> 
> Jakub,
> in Mercurial sequential commit numbers are local to a repo and are not
> unique between the clones. Unique ID is SHA1 as in git. So mercurial
> commit 127:aaf123453dfgdfgddd...
> means commit number 127 in this repo with SHA1 "aaf123453dfgdfgddd..."
> In another clone commit 127 might mean completely different thing.
> Sequential commit numbers are strictly for "local convenience".

To quote his first mail:
	First, you have to remember that this 'number of commit' thingy
	is *local* to your repository, so you cannot use commit numbers
	to communicate with other developers.

With the above example, he has just shown that even with those local
commit numbers, you can't tell that commit X is older than commit Y just
because X < Y.

Björn