format-patch: make "-p" suppress diffstat

Once upon a time, format-patch would use its default stat
plus patch format only when no diff format was given on the
command line. This meant that "format-patch -p" would
suppress the stat and show just the patch.

Commit 68daa64 changed this to keep the stat format when we
had an "implicit" patch format, like "-U5". As a side
effect, this meant that an explicit patch format was now
ignored (because cmd_format_patch didn't know the reason
that the format was set way down in diff_opt_parse).

This patch unbreaks what 68daa64 did (while still preserving
what 68daa64 was trying to do), reinstating "-p" to suppress
the default behavior. We do this by parsing "-p" ourselves
in format-patch, and noting whether it was used explicitly.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-log.c

@@ -891,6 +891,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	struct patch_ids ids;
 	char *add_signoff = NULL;
 	struct strbuf buf = STRBUF_INIT;
+	int use_patch_format = 0;
 	const struct option builtin_format_patch_options[] = {
 		{ OPTION_CALLBACK, 'n', "numbered", &numbered, NULL,
 			    "use [PATCH n/m] even with a single patch",
@@ -920,6 +921,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 			    PARSE_OPT_NOARG | PARSE_OPT_NONEG, keep_callback },
 		OPT_BOOLEAN(0, "no-binary", &no_binary_diff,
 			    "don't output binary diffs"),
+		OPT_BOOLEAN('p', NULL, &use_patch_format,
+			"show patch format instead of default (patch + stat)"),
 		OPT_BOOLEAN(0, "ignore-if-in-upstream", &ignore_if_in_upstream,
 			    "don't include a patch matching a commit upstream"),
 		OPT_GROUP("Messaging"),
@@ -1027,8 +1030,10 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	if (argc > 1)
 		die ("unrecognized argument: %s", argv[1]);
 
-	if (!rev.diffopt.output_format
-		|| rev.diffopt.output_format == DIFF_FORMAT_PATCH)
+	if (use_patch_format)
+		rev.diffopt.output_format |= DIFF_FORMAT_PATCH;
+	else if (!rev.diffopt.output_format ||
+		  rev.diffopt.output_format == DIFF_FORMAT_PATCH)
 		rev.diffopt.output_format = DIFF_FORMAT_DIFFSTAT | DIFF_FORMAT_SUMMARY | DIFF_FORMAT_PATCH;
 
 	if (!DIFF_OPT_TST(&rev.diffopt, TEXT) && !no_binary_diff)

t/t4014-format-patch.sh

@@ -455,6 +455,27 @@ test_expect_success 'format-patch respects -U' '
 
 '
 
+cat > expect << EOF
+
+diff --git a/file b/file
+index 40f36c6..2dc5c23 100644
+--- a/file
++++ b/file
+@@ -14,3 +14,19 @@ C
+ D
+ E
+ F
++5
+EOF
+
+test_expect_success 'format-patch -p suppresses stat' '
+
+	git format-patch -p -2 &&
+	sed -e "1,/^$/d" -e "/^+5/q" < 0001-This-is-an-excessively-long-subject-line-for-a-messa.patch > output &&
+	test_cmp expect output
+
+'
+
 test_expect_success 'format-patch from a subdirectory (1)' '
 	filename=$(
 		rm -rf sub &&