format-patch: clear UNINTERESTING flag before prepare_bases

When users specify the commit range with 'Z..C' pattern for format-patch, all
the parents of Z (including Z) would be marked as UNINTERESTING which would
prevent revision walk in prepare_bases from getting the prerequisite commits,
thus `git format-patch --base <base_commit_sha> Z..C` won't be able to generate
the list of prerequisite patch ids. Clear UNINTERESTING flag with
clear_object_flags solves this issue.
Reported-by: NEduardo Habkost <ehabkost@redhat.com>
Signed-off-by: NXiaolong Ye <xiaolong.ye@intel.com>
Reviewed-by: NStefan Beller <sbeller@google.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/log.c

@@ -1741,6 +1741,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	if (base_commit || base_auto) {
 		struct commit *base = get_base_commit(base_commit, list, nr);
 		reset_revision_walk();
+		clear_object_flags(UNINTERESTING);
 		prepare_bases(&bases, base, list, nr);
 	}
 

t/t4014-format-patch.sh

@@ -1551,13 +1551,15 @@ test_expect_success 'format-patch -o overrides format.outputDirectory' '
 
 test_expect_success 'format-patch --base' '
 	git checkout side &&
-	git format-patch --stdout --base=HEAD~3 -1 | tail -n 7 >actual &&
+	git format-patch --stdout --base=HEAD~3 -1 | tail -n 7 >actual1 &&
+	git format-patch --stdout --base=HEAD~3 HEAD~.. | tail -n 7 >actual2 &&
 	echo >expected &&
 	echo "base-commit: $(git rev-parse HEAD~3)" >>expected &&
 	echo "prerequisite-patch-id: $(git show --patch HEAD~2 | git patch-id --stable | awk "{print \$1}")" >>expected &&
 	echo "prerequisite-patch-id: $(git show --patch HEAD~1 | git patch-id --stable | awk "{print \$1}")" >>expected &&
 	signature >> expected &&
-	test_cmp expected actual
+	test_cmp expected actual1 &&
+	test_cmp expected actual2
 '
 
 test_expect_success 'format-patch --base errors out when base commit is in revision list' '