format-patch: Don't go over merge commits

If the topmost three commits in a branch were merge commits, 'git
format-patch -3' used to output nothing. Since Git can't prepare
patches out of merge commits anyway, don't go over them in the first
place. 'git format-patch -3' now prepares three patches from the
topmost three commits without counting merge commits. Also add a
corresponding test in t4014-format-patch and update documentation.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-format-patch.txt

@@ -73,7 +73,7 @@ OPTIONS
 include::diff-options.txt[]
 
 -<n>::
-	Limits the number of patches to prepare.
+	Prepare patches from the topmost <n> commits.
 
 -o <dir>::
 --output-directory <dir>::

builtin/log.c

@@ -1012,8 +1012,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	rev.commit_format = CMIT_FMT_EMAIL;
 	rev.verbose_header = 1;
 	rev.diff = 1;
-	rev.combine_merges = 0;
-	rev.ignore_merges = 1;
+	rev.no_merges = 1;
 	DIFF_OPT_SET(&rev.diffopt, RECURSIVE);
 	rev.subject_prefix = fmt_patch_subject_prefix;
 	memset(&s_r_opt, 0, sizeof(s_r_opt));
@@ -1184,10 +1183,6 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 			continue;
 		}
 
-		/* ignore merges */
-		if (commit->parents && commit->parents->next)
-			continue;
-
 		if (ignore_if_in_upstream &&
 				has_commit_patch_id(commit, &ids))
 			continue;

t/t4014-format-patch.sh

@@ -56,6 +56,22 @@ test_expect_success "format-patch --ignore-if-in-upstream" '
 
 '
 
+test_expect_success "format-patch doesn't consider merge commits" '
+
+	git checkout -b slave master &&
+	echo "Another line" >>file &&
+	test_tick &&
+	git commit -am "Slave change #1" &&
+	echo "Yet another line" >>file &&
+	test_tick &&
+	git commit -am "Slave change #2" &&
+	git checkout -b merger master &&
+	test_tick &&
+	git merge --no-ff slave &&
+	cnt=`git format-patch -3 --stdout | grep "^From " | wc -l` &&
+	test $cnt = 3
+'
+
 test_expect_success "format-patch result applies" '
 
 	git checkout -b rebuild-0 master &&