Topo-sort before --simplify-merges

This makes the algorithm more honest about what it is doing.

We start from an already limited, topo-sorted list, and postprocess
it by simplifying the irrelevant merges away.

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

revision.c

@@ -1493,6 +1493,8 @@ static void simplify_merges(struct rev_info *revs)
 	struct commit_list *list;
 	struct commit_list *yet_to_do, **tail;
 
+	sort_in_topological_order(&revs->commits, revs->lifo);
+
 	/* feed the list reversed */
 	yet_to_do = NULL;
 	for (list = revs->commits; list; list = list->next)
@@ -1522,9 +1524,6 @@ static void simplify_merges(struct rev_info *revs)
 		if (commit->util == commit)
 			tail = &commit_list_insert(commit, tail)->next;
 	}
-
-	/* sort topologically at the end */
-	sort_in_topological_order(&revs->commits, revs->lifo);
 }
 
 static void set_children(struct rev_info *revs)

t/t6012-rev-list-simplify.sh

@@ -0,0 +1,93 @@
+#!/bin/sh
+
+test_description='merge simplification'
+
+. ./test-lib.sh
+
+note () {
+	git tag "$1"
+}
+
+_x40='[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]'
+_x40="$_x40$_x40$_x40$_x40$_x40$_x40$_x40$_x40"
+
+unnote () {
+	git name-rev --tags --stdin | sed -e "s|$_x40 (tags/\([^)]*\)) |\1 |g"
+}
+
+test_expect_success setup '
+	echo "Hi there" >file &&
+	git add file &&
+	test_tick && git commit -m "Initial file" &&
+	note A &&
+
+	git branch other-branch &&
+
+	echo "Hello" >file &&
+	git add file &&
+	test_tick && git commit -m "Modified file" &&
+	note B &&
+
+	git checkout other-branch &&
+
+	echo "Hello" >file &&
+	git add file &&
+	test_tick && git commit -m "Modified the file identically" &&
+	note C &&
+
+	echo "This is a stupid example" >another-file &&
+	git add another-file &&
+	test_tick && git commit -m "Add another file" &&
+	note D &&
+
+	test_tick && git merge -m "merge" master &&
+	note E &&
+
+	echo "Yet another" >elif &&
+	git add elif &&
+	test_tick && git commit -m "Irrelevant change" &&
+	note F &&
+
+	git checkout master &&
+	echo "Yet another" >elif &&
+	git add elif &&
+	test_tick && git commit -m "Another irrelevant change" &&
+	note G &&
+
+	test_tick && git merge -m "merge" other-branch &&
+	note H &&
+
+	echo "Final change" >file &&
+	test_tick && git commit -a -m "Final change" &&
+	note I
+'
+
+FMT='tformat:%P 	%H | %s'
+
+check_result () {
+	for c in $1
+	do
+		echo "$c"
+	done >expect &&
+	shift &&
+	param="$*" &&
+	test_expect_success "log $param" '
+		git log --pretty="$FMT" --parents $param |
+		unnote >actual &&
+		sed -e "s/^.*	\([^ ]*\) .*/\1/" >check <actual &&
+		test_cmp expect check || {
+			cat actual
+			false
+		}
+	'
+}
+
+check_result 'I H G F E D C B A' --full-history
+check_result 'I H E C B A' --full-history -- file
+check_result 'I H E C B A' --full-history --topo-order -- file
+check_result 'I H E C B A' --full-history --date-order -- file
+check_result 'I E C B A' --simplify-merges -- file
+check_result 'I B A' -- file
+check_result 'I B A' --topo-order -- file
+
+test_done