show -c: show patch text

Traditionally, "show" defaulted to "show --cc" (dense combined patch), but
asking for combined patch with "show -c" didn't turn the patch output
format on; the placement of this logic in setup_revisions() dates back to
cd2bdc5 (Common option parsing for "git log --diff" and friends,
2006-04-14).

This unfortunately cannot be done as a trivial change of "if dense
combined is asked, default to patch format" done in setup_revisions() to
"if any combined is asked, default to patch format", as "diff-tree -c"
needs to default to raw, while "diff-tree --cc" needs to default to patch,
and they share the codepath.  These command specific defaults are now
handled in the new "tweak" callback that can be customized by individual
command implementations.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-diff-tree.c

@@ -92,20 +92,33 @@ static const char diff_tree_usage[] =
 "  --root        include the initial commit as diff against /dev/null\n"
 COMMON_DIFF_OPTIONS_HELP;
 
+static void diff_tree_tweak_rev(struct rev_info *rev, struct setup_revision_opt *opt)
+{
+	if (!rev->diffopt.output_format) {
+		if (rev->dense_combined_merges)
+			rev->diffopt.output_format = DIFF_FORMAT_PATCH;
+		else
+			rev->diffopt.output_format = DIFF_FORMAT_RAW;
+	}
+}
+
 int cmd_diff_tree(int argc, const char **argv, const char *prefix)
 {
 	int nr_sha1;
 	char line[1000];
 	struct object *tree1, *tree2;
 	static struct rev_info *opt = &log_tree_opt;
+	struct setup_revision_opt s_r_opt;
 	int read_stdin = 0;
 
 	init_revisions(opt, prefix);
 	git_config(git_diff_basic_config, NULL); /* no "diff" UI options */
 	opt->abbrev = 0;
 	opt->diff = 1;
 	opt->disable_stdin = 1;
-	argc = setup_revisions(argc, argv, opt, NULL);
+	memset(&s_r_opt, 0, sizeof(s_r_opt));
+	s_r_opt.tweak = diff_tree_tweak_rev;
+	argc = setup_revisions(argc, argv, opt, &s_r_opt);
 
 	while (--argc > 0) {
 		const char *arg = *++argv;
@@ -117,9 +130,6 @@ int cmd_diff_tree(int argc, const char **argv, const char *prefix)
 		usage(diff_tree_usage);
 	}
 
-	if (!opt->diffopt.output_format)
-		opt->diffopt.output_format = DIFF_FORMAT_RAW;
-
 	/*
 	 * NOTE! We expect "a ^b" to be equal to "a..b", so we
 	 * reverse the order of the objects if the second one

builtin-log.c

@@ -327,6 +327,12 @@ static int show_tree_object(const unsigned char *sha1,
 	return 0;
 }
 
+static void show_rev_tweak_rev(struct rev_info *rev, struct setup_revision_opt *opt)
+{
+	if (!rev->diffopt.output_format)
+		rev->diffopt.output_format = DIFF_FORMAT_PATCH;
+}
+
 int cmd_show(int argc, const char **argv, const char *prefix)
 {
 	struct rev_info rev;
@@ -348,6 +354,7 @@ int cmd_show(int argc, const char **argv, const char *prefix)
 	rev.no_walk = 1;
 	memset(&opt, 0, sizeof(opt));
 	opt.def = "HEAD";
+	opt.tweak = show_rev_tweak_rev;
 	cmd_log_init(argc, argv, prefix, &rev, &opt);
 
 	count = rev.pending.nr;

revision.c

@@ -1463,6 +1463,8 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 
 	if (revs->def == NULL)
 		revs->def = opt ? opt->def : NULL;
+	if (opt && opt->tweak)
+		opt->tweak(revs, opt);
 	if (revs->show_merge)
 		prepare_show_merge(revs);
 	if (revs->def && !revs->pending.nr) {
@@ -1496,11 +1498,8 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 		if (!revs->full_diff)
 			diff_tree_setup_paths(revs->prune_data, &revs->diffopt);
 	}
-	if (revs->combine_merges) {
+	if (revs->combine_merges)
 		revs->ignore_merges = 0;
-		if (revs->dense_combined_merges && !revs->diffopt.output_format)
-			revs->diffopt.output_format = DIFF_FORMAT_PATCH;
-	}
 	revs->diffopt.abbrev = revs->abbrev;
 	if (diff_setup_done(&revs->diffopt) < 0)
 		die("diff_setup_done failed");

revision.h

@@ -139,6 +139,7 @@ extern volatile show_early_output_fn_t show_early_output;
 
 struct setup_revision_opt {
 	const char *def;
+	void (*tweak)(struct rev_info *, struct setup_revision_opt *);
 };
 
 extern void init_revisions(struct rev_info *revs, const char *prefix);

t/t4013-diff-various.sh

@@ -238,6 +238,7 @@ show initial
 show --root initial
 show side
 show master
+show -c master
 show --stat side
 show --stat --summary side
 show --patch-with-stat side

t/t4013/diff.show_-c_master

@@ -0,0 +1,36 @@
+$ git show -c master
+commit 59d314ad6f356dd08601a4cd5e530381da3e3c64
+Merge: 9a6d494 c7a2ab9
+Author: A U Thor <author@example.com>
+Date:   Mon Jun 26 00:04:00 2006 +0000
+
+    Merge branch 'side'
+
+diff --combined dir/sub
+index cead32e,7289e35..992913c
+--- a/dir/sub
++++ b/dir/sub
+@@@ -1,6 -1,4 +1,8 @@@
+  A
+  B
+ +C
+ +D
+ +E
+ +F
++ 1
++ 2
+diff --combined file0
+index b414108,f4615da..10a8a9f
+--- a/file0
++++ b/file0
+@@@ -1,6 -1,6 +1,9 @@@
+  1
+  2
+  3
+ +4
+ +5
+ +6
++ A
++ B
++ C
+$