Re: Mercurial vs Updated git HOWTO for kernel hackers

[Linus Torvalds <torvalds@osdl.org>]

On Fri, 24 Jun 2005, Matthias Urlichs wrote:
> 
> Well, I don't. Main reason: It's simply a lot faster to create+switch to a
> branch locally for doing independent work, than to hardlink the whole
> Linux directory tree into a clone tree.
> 
> Having one tree also simpifies the "what do I have that's not merged yet"
> question -- just call "gitk $(cat .git/refs/heads/*)". ;-)

Actually, I think that gets close to another real advantage of branches:  
that is also what allows you to edit things that failed a merge.

For example, let's say that a merge fail. You've got the HEAD and the
MERGE_HEAD, but a file type conflict (like a symlink that has turned into
a directory) or something like that means that you can't resolve them
sanely at all.

So this is merge problem where you can't just do a three-way merge and fix 
up the result and commit: you have to fix things up before you can even 
really do the merge. This is when switching to the MERGE_HEAD thing and 
fixing it up there, committing it, and then doing the merge with the 
original HEAD and the new MERGE_HEAD is really convenient.

(No, the scripts don't help you in cases like this, and we don't do the
MERGE_HEAD as a real branch right now, but the point is that we _can_, and
that this is more than an efficiency issue, it's a fundamental issue of
working with multiple end-points together. You _could_ clone the other 
head into a totally new repository, fix it there, and then try the merge 
anew, but now you're working around a limitation, not just doing 
something slower).

I still think you can go a bit too far on your branch usage (ie Jeff), but 
hey, what's the difference between three branches and fifty, really?

(I'm kidding. The difference between three and fifty is how well you can 
keep track of them in your head, but maybe Jeff just has a bigger head 
than most people do. Jeff, do people go "Boy, you've got a big head" the 
first time they meet you?)

			Linus
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