Why does git merge have so much trouble with Fedora package branches?

[Simo Sorce]

On Thu, 2011-11-10 at 10:52 +0100, Fabian Deutsch wrote:
> Am Donnerstag, den 10.11.2011, 10:36 +0100 schrieb Vratislav Podzimek:
> > On Wed, 2011-11-09 at 18:48 -0800, Adam Williamson wrote:
> > > On Thu, 2011-11-10 at 10:29 +0800, Mathieu Bridon wrote:
> > > > On Wed, 2011-11-09 at 21:20 -0500, Simo Sorce wrote:
> > > > > On Wed, 2011-11-09 at 17:46 -0800, Adam Williamson wrote:
> > > > > > I'm currently going through and bumping several packages whose Rawhide
> > > > > > builds have got behind their F16 builds.
> > > > > > 
> > > > > > I've come across several packages where git merge hit 'conflicts' for no
> > > > > > readily apparently reason in this case.
> > > > > 
> > > > > I haven't looked deeply enough to tell, but in general merges are a very
> > > > > bad tool and should be avoid IMHO.
> > > > > 
> > > > > It would be much more sane to git cherry-pick the changes you need and
> > > > > keep the branches separate and have their own history.
> > > > > Merges makes it really painful to follow history later.
> > > > 
> > > > I agree. Once branches have started to diverge, merging them makes the
> > > > history harder to follow because the branches keep diverging, merging
> > > > back, diverging again, merging,...
> > > > 
> > > > However, it is sometimes possible to never diverge.
> > > > 
> > > > In the example of gnome-power-manager, the master and f16 branches seem
> > > > to contain the exact same changes, in the same order.
> > > > 
> > > > In such a case, it would have made sense to always keep merging the
> > > > branches rather than cherry-picking, so that they would never have
> > > > diverged.
> > > > 
> > > > And that would have avoided the conflict Adam is seeing.
> > > 
> > > thanks both of you; I hadn't really thought about the consequences of
> > > merging vs. cherry-picking, I think I'd just cargo-culted from somewhere
> > > the idea of using git merge instead of manually re-doing changes without
> > > considering cherry-picking instead. so I guess in general it's both a
> > > better idea and more likely to work to use cherry-pick instead of merge,
> > > unless the two branches are really expected to be identical?
> > Isn't it better to use 'git rebase'? E.g. on master use 'git rebase
> > f16'. As I understand it, it would do the same as cherry-picking commit
> > after commit in these cases.
> 
> Someone might correct me, but rebasing introduces problems for
> co-maintainers, if upstream (maintainer) decides to rebase some branch.

Only if you rewrite history. For forwards it does not cause any issue.

Simo.

-- 
Simo Sorce * Red Hat, Inc * New York