Fix --cherry-pick with given paths

If you say --cherry-pick, you do not want to see patches which are
in the upstream.  If you specify paths with that, what you usually
expect is that only those parts of the patches are looked at which
actually touch the given paths.

With this patch, that expectation is met.

Noticed by Sam Vilain.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

revision.c

@@ -437,7 +437,7 @@ static int add_parents_to_list(struct rev_info *revs, struct commit *commit, str
 	return 0;
 }
 
-static void cherry_pick_list(struct commit_list *list)
+static void cherry_pick_list(struct commit_list *list, struct rev_info *revs)
 {
 	struct commit_list *p;
 	int left_count = 0, right_count = 0;
@@ -458,6 +458,11 @@ static void cherry_pick_list(struct commit_list *list)
 
 	left_first = left_count < right_count;
 	init_patch_ids(&ids);
+	if (revs->diffopt.nr_paths) {
+		ids.diffopts.nr_paths = revs->diffopt.nr_paths;
+		ids.diffopts.paths = revs->diffopt.paths;
+		ids.diffopts.pathlens = revs->diffopt.pathlens;
+	}
 
 	/* Compute patch-ids for one side */
 	for (p = list; p; p = p->next) {
@@ -546,7 +551,7 @@ static int limit_list(struct rev_info *revs)
 		p = &commit_list_insert(commit, p)->next;
 	}
 	if (revs->cherry_pick)
-		cherry_pick_list(newlist);
+		cherry_pick_list(newlist, revs);
 
 	revs->commits = newlist;
 	return 0;

t/t6007-rev-list-cherry-pick-file.sh

@@ -0,0 +1,43 @@
+#!/bin/sh
+
+test_description='test git rev-list --cherry-pick -- file'
+
+. ./test-lib.sh
+
+# A---B
+#  \
+#   \
+#    C
+#
+# B changes a file foo.c, adding a line of text.  C changes foo.c as
+# well as bar.c, but the change in foo.c was identical to change B.
+
+test_expect_success setup '
+	echo Hallo > foo &&
+	git add foo &&
+	test_tick &&
+	git commit -m "A" &&
+	git tag A &&
+	git checkout -b branch &&
+	echo Bello > foo &&
+	echo Cello > bar &&
+	git add foo bar &&
+	test_tick &&
+	git commit -m "C" &&
+	git tag C &&
+	git checkout master &&
+	git checkout branch foo &&
+	test_tick &&
+	git commit -m "B" &&
+	git tag B
+'
+
+test_expect_success '--cherry-pick foo comes up empty' '
+	test -z "$(git rev-list --left-right --cherry-pick B...C -- foo)"
+'
+
+test_expect_success '--cherry-pick bar does not come up empty' '
+	! test -z "$(git rev-list --left-right --cherry-pick B...C -- bar)"
+'
+
+test_done