Re: The merge from hell...

From: Linus Torvalds <torvalds@osdl.org>
Date: Feb 4, 2006, 19:42 UTC
Message-ID: <Pine.LNX.4.64.0602041125440.3854@g5.osdl.org>
In-Reply-To: <17380.34301.584514.520465@cargo.ozlabs.ibm.com>

On Sat, 4 Feb 2006, Paul Mackerras wrote:

Show 16 quoted lines

> 
> > But this is still interesting:
> > 
> > @@@@@@@@@@@@@ +308,35 @@@@@@@@@@@@@
> >             			goto end;
> >             		}
> >             	}
> >   --        	cx->usage++;
> >   --        
> >             
> >      +++    #ifdef CONFIG_HOTPLUG_CPU
> >      +++    	/*
> 
> Why is that interesting?  It seems to me that two independent changes
> were made that just happened to be within a couple of lines of each
> other, but didn't interact.

Correct. It's "interesting" only because the context of three lines overlapped. So _technically_ it's not that interesting.

> The reason that one change appears in two branches, and the other in 3, 
> is I think just related to where the branches start from.  So IMHO this 
> hunk isn't interesting.

I actually think that whenever there are edits this close (even if they aren't strictly overlapping) they actually _are_ interesting. Even if it merged automatically, you may well want to know that the automated merge did something like this.

Doing a

	git-rev-list --parents HEAD |
		egrep '^.{90}' |
		cut -d' ' -f1 | 
		git-diff-tree --pretty --cc --stdin
		| less -S

on the kernel is actually interesting. It's interesting because it shows that out of 1391 merges, in the kernel, only _19_ actually had these close calls. Some - but certainly not all - of them actually did need manual fixup.

So I actually prefer the "show close misses" case. But I guess we could have a "-cN" line to tell how many lines of context to use..

		Linus