Re: antisocial things you can do in git (but not CVS)

On Tue, Jul 20, 2010 at 2:42 PM, Magnus Hagander <magnus@hagander.net> wrote:
> On Tue, Jul 20, 2010 at 20:34, Robert Haas <robertmhaas@gmail.com> wrote:
>> I have some concerns related to the upcoming conversion to git and how
>> we're going to avoid having things get messy as people start using the
>> new repository.  git has a lot more flexibility and power than CVS,
>> and I'm worried that it would be easy, even accidentally, to screw up
>> our history.
>>
>> 1. Inability to cleanly and easily (and programatically) identify who
>> committed what.  With CVS, the author of a revision is the person who
>> committed it, period.  With git, the author string can be set to
>> anything the person typing 'git commit' feels like.  I think there is
>> also a committer field, but that doesn't always appear and I'm not
>> clear on how it works.  Also, the author field defaults to something
>> dumb if you don't explicitly set it to a value.  So I'm worried we
>> could end up with stuff like this in the repository:
>
> I'm pretty sure we can enforce this on the server side, refusing
> commits that don't follow our standard. I haven't done it myself
> (yet), but I've read about it.

+1, though I see downthread that Peter has a contrary opinion.

>> My preference would be to stick to a style where we identify the
>> committer using the author tag and note the patch author, reviewers,
>> whether the committer made changes, etc. in the commit message.  A
>> single author field doesn't feel like enough for our workflow, and
>> having a mix of authors and committers in the author field seems like
>> a mess.
>
> +1.
>
>
>> 2. Branch and tag management.  In CVS, there are branches and tags in
>> only one place: on the server.  In git, you can have local branches
>> and tags and remote branches and tags, and you can pull and push tags
>> between servers.  If I'm working on a git repository that has branches
>> master, REL9_0_STABLE .. REL7_4_STABLE, inner_join_removal,
>> numeric_2b, and temprelnames, I want to make sure that I don't
>> accidentally push the last three of those to the authoritative
>> server... but I do want to push all the others.  Similarly I want to
>> push only the corrects subset of tags (though that should be less of
>> an issue, at least for me, as I don't usually create local tags).  I'm
>> not sure how to set this up, though.
>
> We could put a safeguard in place on the server that won't let you
> push a branch and require that additions of new branches be done
> manually on the server?

On this one, I'd just like a way to prevent accidents.  Is there maybe
a config option I can set on my local repository?

>> 3. Merge commits.  I believe that we have consensus that commits
>> should always be done as a "squash", so that the history of all of our
>> branches is linear.  But it seems to me that someone could
>> accidentally push a merge commit, either because they forgot to squash
>> locally, or because of a conflict between their local git repo's
>> master branch and origin/master.  Can we forbid this?
>
> Again, I haven't done it, but I've read about it, and I'm almost
> certain we can enforce this, yes.

OK, that sounds good...

>> 4. History rewriting.  Under what circumstances, if any, are we OK
>> with rebasing the master?  For example, if we decide not to have merge
>> commits, and somebody does a merge commit anyway, are we going to
>> rebase to get rid of it?
>
> That's something we need a good policy for. Merge commits are special.
> For content commits, I think we should basically *never* do that. If
> someone commits bad content, we should just make a revert commit which
> keeps history linear and just removes the changes as a new commit.

Yeah, I agree.  I'm not sure that merge commits are the ONLY situation
where we'd want to do this, but it should be reserved for cases where
just reversing out the diff wouldn't be sufficient for some reason and
we need to make it as though it never happened.  I don't think it's
probably necessary to disallow this completely - the default setting
of allowing it only with + is probably enough.

--
Robert Haas
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