merge/pull: add the "--compact-summary" option

"git merge" and "git pull" shows "git diff --stat --summary @{1}"
when they finish to indicate the extent of the changes brought into
the history by default.  While it gives a good overview, it becomes
annoying when there are very many created or deleted paths.

Introduce "--compact-summary" option to these two commands that
tells it to instead show "git diff --compact-summary @{1}", which
gives the same information in a lot more compact form in such a
situation.

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

Documentation/git-merge.adoc

@@ -9,7 +9,7 @@ git-merge - Join two or more development histories together
 SYNOPSIS
 --------
 [synopsis]
-git merge [-n] [--stat] [--no-commit] [--squash] [--[no-]edit]
+git merge [-n] [--stat] [--compact-summary] [--no-commit] [--squash] [--[no-]edit]
 	[--no-verify] [-s <strategy>] [-X <strategy-option>] [-S[<keyid>]]
 	[--[no-]allow-unrelated-histories]
 	[--[no-]rerere-autoupdate] [-m <msg>] [-F <file>]

Documentation/merge-options.adoc

@@ -113,6 +113,9 @@ include::signoff-option.adoc[]
 With `-n` or `--no-stat` do not show a diffstat at the end of the
 merge.
 
+`--compact-summary`::
+	Show a compact-summary at the end of the merge.
+
 `--squash`::
 `--no-squash`::
 	Produce the working tree and index state as if a real merge

builtin/merge.c

@@ -69,7 +69,10 @@ static const char * const builtin_merge_usage[] = {
 	NULL
 };
 
-static int show_diffstat = 1, shortlog_len = -1, squash;
+#define MERGE_SHOW_DIFFSTAT 1
+#define MERGE_SHOW_COMPACTSUMMARY 2
+
+static int show_diffstat = MERGE_SHOW_DIFFSTAT, shortlog_len = -1, squash;
 static int option_commit = -1;
 static int option_edit = -1;
 static int allow_trivial = 1, have_message, verify_signatures;
@@ -243,12 +246,28 @@ static int option_parse_strategy(const struct option *opt UNUSED,
 	return 0;
 }
 
+static int option_parse_compact_summary(const struct option *opt,
+					const char *name UNUSED, int unset)
+{
+	int *setting = opt->value;
+
+	if (unset)
+		*setting = 0;
+	else
+		*setting = MERGE_SHOW_COMPACTSUMMARY;
+	return 0;
+}
+
 static struct option builtin_merge_options[] = {
 	OPT_SET_INT('n', NULL, &show_diffstat,
 		N_("do not show a diffstat at the end of the merge"), 0),
 	OPT_BOOL(0, "stat", &show_diffstat,
 		N_("show a diffstat at the end of the merge")),
 	OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
+	OPT_CALLBACK_F(0, "compact-summary", &show_diffstat, N_("compact-summary"),
+		       N_("show a compact-summary at the end of the merge"),
+		       PARSE_OPT_NOARG,
+		       option_parse_compact_summary),
 	{
 		.type = OPTION_INTEGER,
 		.long_name = "log",
@@ -494,8 +513,19 @@ static void finish(struct commit *head_commit,
 		struct diff_options opts;
 		repo_diff_setup(the_repository, &opts);
 		init_diffstat_widths(&opts);
-		opts.output_format |=
+
-			DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
+		switch (show_diffstat) {
+		case MERGE_SHOW_DIFFSTAT: /* 1 */
+			opts.output_format |=
+				DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
+			break;
+		case MERGE_SHOW_COMPACTSUMMARY: /* 2 */
+			opts.output_format |= DIFF_FORMAT_DIFFSTAT;
+			opts.flags.stat_with_summary = 1;
+			break;
+		default:
+			break;
+		}
 		opts.detect_rename = DIFF_DETECT_RENAME;
 		diff_setup_done(&opts);
 		diff_tree_oid(head, new_head, "", &opts);
@@ -643,7 +673,8 @@ static int git_merge_config(const char *k, const char *v,
 	}
 
 	if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat")) {
-		show_diffstat = git_config_bool(k, v);
+		show_diffstat = git_config_bool(k, v)
+			? MERGE_SHOW_DIFFSTAT : 0;
 	} else if (!strcmp(k, "merge.verifysignatures")) {
 		verify_signatures = git_config_bool(k, v);
 	} else if (!strcmp(k, "pull.twohead")) {

builtin/pull.c

@@ -143,6 +143,9 @@ static struct option pull_options[] = {
 	OPT_PASSTHRU(0, "summary", &opt_diffstat, NULL,
 		N_("(synonym to --stat)"),
 		PARSE_OPT_NOARG | PARSE_OPT_HIDDEN),
+	OPT_PASSTHRU(0, "compact-summary", &opt_diffstat, NULL,
+		N_("show a compact-summary at the end of the merge"),
+		PARSE_OPT_NOARG),
 	OPT_PASSTHRU(0, "log", &opt_log, N_("n"),
 		N_("add (at most <n>) entries from shortlog to merge commit message"),
 		PARSE_OPT_OPTARG),

t/t7600-merge.sh

@@ -185,8 +185,19 @@ test_expect_success 'reject non-strategy with a git-merge-foo name' '
 test_expect_success 'merge c0 with c1' '
 	echo "OBJID HEAD@{0}: merge c1: Fast-forward" >reflog.expected &&
 
+	cat >expect <<-\EOF &&
+	Updating FROM..TO
+	Fast-forward
+	 file  | 2 +-
+	 other | 9 +++++++++
+	 2 files changed, 10 insertions(+), 1 deletion(-)
+	 create mode 100644 other
+	EOF
+
 	git reset --hard c0 &&
-	git merge c1 &&
+	git merge c1 >out &&
+	sed -e "1s/^Updating [0-9a-f.]*/Updating FROM..TO/" out >actual &&
+	test_cmp expect actual &&
 	verify_merge file result.1 &&
 	verify_head "$c1" &&
 
@@ -205,6 +216,21 @@ test_expect_success 'merge c0 with c1 with --ff-only' '
 	verify_head "$c1"
 '
 
+test_expect_success 'the same merge with compact summary' '
+	cat >expect <<-\EOF &&
+	Updating FROM..TO
+	Fast-forward
+	 file        | 2 +-
+	 other (new) | 9 +++++++++
+	 2 files changed, 10 insertions(+), 1 deletion(-)
+	EOF
+
+	git reset --hard c0 &&
+	git merge --compact-summary c1 >out &&
+	sed -e "1s/^Updating [0-9a-f.]*/Updating FROM..TO/" out >actual &&
+	test_cmp expect actual
+'
+
 test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge from unborn branch' '