[Python-Dev] I am now lost - committed, pulled, merged, what is "collapse"?

[Stephen J. Turnbull]

R. David Murray writes:

 > The workflow in svn "can" "require" this same thing:  before committing,
 > you do an svn up and run the test suite.

No, it can't.  That's not good enough, if you care about tree-wide
consistency, because svn's approach has a race condition.  You say you
don't care, but for many, that was an artifact of svn's inability to
enforce tree-wide up-to-dateness, and they don't want to go back (see
Hrvoje's post).  If you say that is *not* Python project policy, OK,
neither Hrvoje nor I claim to determine policy.

 > That is, not only did the change in the tool and consequent change in
 > the workflow have *zero* impact on this aspect of the way I work with
 > CPython, it didn't even trigger me to *think* about it.

That's too bad, because now there often is a better way.  If you think
you're ready to merge, then commit, merge, and run the tests *after*
the merge.  You still have an untested revision in the DAG, but it
will not be tip.  If the tests fail, update, lather, rinse, repeat.

This won't be pleasant if people are sprinting and lots of commits are
coming, because you're likely to repeatedly lose the push race.  But
in those conditions, nothing is guaranteed to work in decentralized
fashion (that's one reason why the Linux kernel uses Linus and
lieutenants as a serialization mechanism).