Re: git-bisect not working correctly in the kvm.git repository?

[Linus Torvalds <torvalds@linux-foundation.org>]

On Mon, 17 Nov 2008, walt wrote:
>
> I'm trying to find a bug introduced somewhere between kvm-69
> and kvm-70, so of course I want to git-bisect down to it.
> 
> The weirdness is that when I give git-bisect the good and
> bad tags, almost everything in my working directory just
> disappears, leaving only the qemu subdirectory behind.

Have you done subdirectory merges or other odd merges?

If you merge stuff from another project that isn't a full repository, then 
you are merging commits that simply don't _have_ the full tree of your 
repo. If you then bisect into those commits, the checkout will then (of 
course) end up having only the files that are in that partial tree.

This will happen in the git repository too, if "git bisect" ends up 
jumping into one of the commits that were done in the 'gitk' repository. 

For an example of this, do something like

	git clean -dqfx
	git checkout -b oddbranch eb33a67f218b612f6fb1456e19b40a1f97ff02c0

in the git repository, and see all files disappear, and gitk is no longer 
in the 'gitk-git' subdirectory, but got moved to the top level.

Because in the history that is that commit, that is literally how things 
were. The data from that commit just got merged into a subdirectory of its 
own, and together with all the rest of git, by using a subtree merge.

			Linus