Re: [PATCH 3/3] diff-index: pass pathspec down to unpack-trees machinery

Jonathan Nieder [off-list ref] writes:

Junio C Hamano wrote:

quoted

And finally, pass the pathspec down through unpack_trees() to traverse_trees()
callchain.

In git versions which include the patch described above, the unchanged
subdir/hello.h shows up as a newly added file.  Reverting that patch
(v1.7.7.1~22^2, diff-index: pass pathspec down to unpack-trees
machinery, 2011-08-29) makes "git diff HEAD" with wildcards work
again.

I suspect that the particular change on the side branch predates Nguyen's
effort to unify the pathspec semantics to teach the wildcard (i.e. not the
traditional "prefix match") to the tree traversal code, but it is fairly
late here, so I didn't check.

I think the right fix is to update the logic that still assumes that a
pathspec used for tree traversal is always prefix match when leaving the
traversal early, and instead use the proper matching logic that knows that
a wildcard pathspec needs to dig deeper into the tree regardless (I think
the pathspec implementation used in "git grep" got this right, but please
double check), so that we do not dig unnecessary subtrees when pathspecs
are all prefixes, but still keep digging when there is a wildcard match.

I suspect that it would lead to a fairly complete unification of the three
implementations of pathspec matching logic and would allow us to also do
something like "git log -- '*.h'" for free.