Re: [PATCH 3/3] Avoid doing extra 'lstat()'s for d_type if we have an up-to-date cache entry

Linus Torvalds [off-list ref] writes:

We don't really verify the whole path when we mark things ce_uptodate(). 
Part of what read_directory() does is to find directory entries, and in 
the process things like "git add" will notice if there's a conflict with 
existing index entries.

So if a directory has changed into a symlink to a directory, this 
particular optimization will actually hide that, I suspect. I haven't 
tested, though. But it might be worth-while to see what happens when you 
had a directory structure, and then do

	mkdir dir
	touch dir/a
	touch dir/b
	git add dir

	mv dir new-dir
	ln -s new-dir dir
	git status

In existing codepaths, we have "has_symlink_leading_path()" checks to
notice that tracked dir/[ab] have disappeared.  "git diff" before or after
"git status" in the above sequence does notice what you did.

Would dir/a be marked as uptodate in the index, if somebody preloads the
index, after the above sequence?  I hope not.