Re: [alsa-devel] HG -> GIT migration

[Takashi Iwai]

At Wed, 21 May 2008 12:02:29 -0700 (PDT),
Linus Torvalds wrote:
> 
> On Wed, 21 May 2008, Takashi Iwai wrote:
> > 
> > >  - cherry-pick it. Is it a small, simple patch that you want, but that 
> > >    isn't really worth pulling in all the other stuff that you simply don't 
> > >    know?
> > > 
> > >    This isn't wrong. It shouldn't be *common*, but it's not wrong to have 
> > >    the same patch in two different branches. It makes sense if it is 
> > >    something you really want, but it's still not important or complex 
> > >    enough to actually mege everything else!
> > 
> > Hm, that's what I didn't consider seriously.  I thought cherry-picking
> > patches may cause merge errors easily.
> 
> Cherry-picking can certainly cause merge errors, but not generally very 
> often.
> 
> Cherry-picking by definition will obviously apply the *same* patch to two 
> different branches, and as a result, when you merge, that merge will 
> generally be totally clean. So a trivial merge that succeeds without you 
> even noticing is actually the common case.
> 
> But you can certainly get merge failures where you then have to fix things 
> up if there were *other* changes to that same area. At that point, you end 
> up with two different branches that changed the same few lines 
> differently, and it doesn't matter if then _some_ of the changes were 
> identical - the fact that others were not is enough to cause a merge 
> conflict.
> 
> If cherry-picking is an uncommon situation, the merge problems are not 
> going to show up (and when they do, they'll generally be simple to 
> resolve, especially if you limit cherry-picking to simple fixes). But if 
> you do a *lot* of cherry-picking, and you cherry-pick big changes, then 
> yes, you'll start hitting merge problems.
> 
> So cherry-picking is fine if you do it (a) fairly seldom and (b) just to 
> small patches, because then the upsides of cherry-picking (easy to get a 
> single fix without merging everything else) are bigger than the downsides 
> (the potential merge problems later).
> 
> IOW, think of cherry-picking as just another tool. It has upsides and 
> downsides. It's not "wrong" per se, but you can use it the wrong way. You 
> shouldn't use a hammer on a screw, and you shouldn't use cherry-picking 
> for big and complex stuff.

Thanks for clarification!

Sounds like I should really do this more often to keep the devel tree
clean without merge or rebase.


Takashi
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