"fatal: Untracked working tree file 'so-and-so' would be overwritten by merge"

[Linus Torvalds <torvalds@osdl.org>]

Hmm. I'm getting this message annoyingly often, simply because a few files 
that used to be tracked are now generated, and so they exist in my tree 
but are no longer tracked.

However, they may be tracked in an older tree that I pull, because in that 
older tree they _do_ exist, and we get the

	fatal: Untracked working tree file 'so-and-so' would be overwritten by merge.

which is actually incorrect, because the merge result will not even 
_contain_ that untracked file any more.

So the message is misleading - we should only consider this a fatal thing 
if we actually do generate that file as part of a git-read-tree, but if a 
merge won't touch a file, it shouldn't be "overwritten".

It's true that if the _other_ end actually removed a file that we used to 
have (ie the file _disappears_ as part of the merge), then we should 
verify that that file matched what we're going to remove, but if the old 
index didn't contain the file at all, and the new index won't contain it 
either, it really should be a no-op.

IOW, I think there is one "verify_absent()" too many somewhere, where we 
check this unnecessarily. I think it's the one in "deleted_entry()" in 
unpack-trees.c, but I'm not sure.

		Linus