merge --stat: use the full terminal width

Make merge --stat behave like diff --stat and use the full terminal
width.

Signed-off-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/merge.c

@@ -399,6 +399,7 @@ static void finish(struct commit *head_commit,
 	if (new_head && show_diffstat) {
 		struct diff_options opts;
 		diff_setup(&opts);
+		opts.stat_width = -1; /* use full terminal width */
 		opts.output_format |=
 			DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 		opts.detect_rename = DIFF_DETECT_RENAME;

t/t4052-stat-output.sh

@@ -168,19 +168,19 @@ respects expect200 log -1 --stat
 EOF
 
 cat >expect <<'EOF'
- abcd | 1000 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ abcd | 1000 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 EOF
-test_expect_success 'merge --stat ignores COLUMNS (big change)' '
+test_expect_success 'merge --stat respects COLUMNS (big change)' '
 	git checkout -b branch HEAD^^ &&
 	COLUMNS=100 git merge --stat --no-ff master^ >output &&
 	grep " | " output >actual
 	test_cmp expect actual
 '
 
 cat >expect <<'EOF'
- ...aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa | 1000 ++++++++++++++++++++
+ ...aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa | 1000 ++++++++++++++++++++++++++++++++++++++++
 EOF
-test_expect_success 'merge --stat ignores COLUMNS (long filename)' '
+test_expect_success 'merge --stat respects COLUMNS (long filename)' '
 	COLUMNS=100 git merge --stat --no-ff master >output &&
 	grep " | " output >actual
 	test_cmp expect actual