[PATCH v2 19/19] reset [--mixed]: use diff-based reset whether or not pathspec was given

[Martin von Zweigbergk <martinvonz@gmail.com>]

Thanks to b65982b (Optimize "diff-index --cached" using cache-tree,
2009-05-20), resetting with paths is much faster than resetting
without paths. Some timings for the linux-2.6 repo to illustrate this
(best of five, warm cache):

        reset       reset .
real    0m0.219s    0m0.080s
user    0m0.140s    0m0.040s
sys     0m0.070s    0m0.030s

These two commands should do the same thing, so instead of having the
user type the trailing " ." to get the faster do_diff_cache()-based
implementation, always use it when doing a mixed reset, with or
without paths (so "git reset $rev" would also be faster).

Timing "git reset" shows that it indeed becomes as fast as
"git reset ." after this patch.

Signed-off-by: Martin von Zweigbergk <martinvonz@gmail.com>
---
It seems like a better solution would be for unpack_trees() learn the
same tricks as do_diff_cache(). I'm leaving that a challange for the
reader :-). I did have a look a unpack_trees(), but it looked rather
overwhelming.

 builtin/reset.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/builtin/reset.c b/builtin/reset.c
index 45b01eb..921afbe 100644
--- a/builtin/reset.c
+++ b/builtin/reset.c
@@ -322,7 +322,7 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 	if (reset_type != SOFT) {
 		struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 		int newfd = hold_locked_index(lock, 1);
-		if (pathspec) {
+		if (reset_type == MIXED) {
 			if (read_from_tree(pathspec, sha1))
 				return 1;
 		} else {
-- 
1.8.1.1.454.gce43f05