format-patch: support format.mboxrd with --stdout

mboxrd is a more robust output format when used with --stdout
and needs more exposure.  Introducing this config knob lets
users choose the more robust format for all their --stdout
uses.

Relying on --pretty=mboxrd and including all of pretty-formats.txt
in the `git format-patch' documentation would likely be
confusing to users.  Furthermore, this setting is useful across
multiple invocations.  So introduce `format.mboxrd' as a boolean
configuration knob that changes the default --pretty=email format
to --pretty=mboxrd when (and only when) --stdout is in use.

Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config/format.txt

@@ -139,3 +139,7 @@ For example,
 ------------
 +
 will only show notes from `refs/notes/bar`.
+
+format.mboxrd::
+	A boolean value which enables the robust "mboxrd" format when
+	`--stdout` is in use to escape "^>+From " lines.

builtin/log.c

@@ -52,6 +52,7 @@ static int decoration_style;
 static int decoration_given;
 static int use_mailmap_config = 1;
 static unsigned int force_in_body_from;
+static int stdout_mboxrd;
 static const char *fmt_patch_subject_prefix = "PATCH";
 static int fmt_patch_name_max = FORMAT_PATCH_NAME_MAX_DEFAULT;
 static const char *fmt_pretty;
@@ -1077,6 +1078,10 @@ static int git_format_config(const char *var, const char *value, void *cb)
 		cover_from_description_mode = parse_cover_from_description(value);
 		return 0;
 	}
+	if (!strcmp(var, "format.mboxrd")) {
+		stdout_mboxrd = git_config_bool(var, value);
+		return 0;
+	}
 
 	return git_log_config(var, value, cb);
 }
@@ -2105,6 +2110,9 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 				  rev.diffopt.close_file, "--output",
 				  !!output_directory, "--output-directory");
 
+	if (use_stdout && stdout_mboxrd)
+		rev.commit_format = CMIT_FMT_MBOXRD;
+
 	if (use_stdout) {
 		setup_pager();
 	} else if (!rev.diffopt.close_file) {

t/t4014-format-patch.sh

@@ -2281,7 +2281,7 @@ test_expect_success 'format-patch --attach cover-letter only is non-multipart' '
 	test_line_count = 1 output
 '
 
-test_expect_success 'format-patch --pretty=mboxrd' '
+test_expect_success '-c format.mboxrd format-patch' '
 	sp=" " &&
 	cat >msg <<-INPUT_END &&
 	mboxrd should escape the body
@@ -2316,7 +2316,9 @@ test_expect_success 'format-patch --pretty=mboxrd' '
 	INPUT_END
 
 	C=$(git commit-tree HEAD^^{tree} -p HEAD <msg) &&
-	git format-patch --pretty=mboxrd --stdout -1 $C~1..$C >patch &&
+	git -c format.mboxrd format-patch --stdout -1 $C~1..$C >patch &&
+	git format-patch --pretty=mboxrd --stdout -1 $C~1..$C >compat &&
+	test_cmp patch compat &&
 	git grep -h --no-index -A11 \
 		"^>From could trip up a loose mbox parser" patch >actual &&
 	test_cmp expect actual

t/t4150-am.sh

@@ -1033,7 +1033,7 @@ test_expect_success 'am --patch-format=mboxrd handles mboxrd' '
 	>From extra escape for reversibility
 	INPUT_END
 	git commit -F msg &&
-	git format-patch --pretty=mboxrd --stdout -1 >mboxrd1 &&
+	git -c format.mboxrd format-patch --stdout -1 >mboxrd1 &&
 	grep "^>From could trip up a loose mbox parser" mboxrd1 &&
 	git checkout -f first &&
 	git am --patch-format=mboxrd mboxrd1 &&