Re: SCMS question

"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
>> Yes, it's nice. Consider this: Andrew develops some changes to PL/perl
>> in his branch. Neil doesn't like something in those changes, so he
>> commits a fix there. In the meantime, Tom has been busy with his own
>> stuff and committing to the main branch; Andrew can track those changes
>> by propagating from the main branch to his branch -- he doesn't need to
>> fall behind and update his modified tree once a month and deal with
>> umpteen conflicts.
>
> Yah know, the one bit of these pitches that always sounds like pure
> snake oil is the claim that they offer some kind of mechanical solution
> to merge conflicts. AFAICS that has nothing to do with the SCMS in use
> and everything to do with whether your "diff" command is AI-complete.

Well there is some difference in that it's easier to do that when you have the
common ancestor.

But it has more to do with being able to see the changes other people are
making. In the above scenario imagine Neil had just emailed the fix and Andrew
hadn't seen it for a week. Or more importantly that Neil had emailed the fix
and someone else had also emailed a different fix somewhere else. Because they
couldn't see each others changes they have no idea when they're generating the
patch that they're generating it against old versions.

> I note also that CVS does have the ability to merge changes across
> branches, we just choose not to use it that way.

And the reason why, I assume, is because it's hard to grant access to CVS
without granting access to do anything at all to the whole repository. And CVS
is fragile enough that that's pretty scary. There are lots of ways someone
could mess up a CVS repository.

The distributed systems sound neat and do sound like they match our style of
working. But they seem like a big leap for a project that's still using a
buggy unmaintained pile of spaghetti code for fear of change. Subversion is
the path of least resistance in that nothing has to change, we can choose to
use new features if we want but otherwise it's basically a CVS 2.0 with a new
name (and active maintenance).

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com