commit - 2afa256de5f9027b941e0a912d57fa5201a6cfc6
commit + 83e5e9a11730a93d948aabbafdb2592713eb6f28
blob - 0b7ff7916ba48b09d48cbc1c37cf75175316b469
blob + ee41732e49ededaf4c54218c0d0b9deb2c1feff9
--- got/got.1
+++ got/got.1
@@ -890,7 +890,7 @@ and gives no special significance to the location of p
 in a pattern.
 .It Xo
 .Cm log
-.Op Fl bdPpRs
+.Op Fl bdPpRst
 .Op Fl C Ar number
 .Op Fl c Ar commit
 .Op Fl l Ar N
@@ -1038,6 +1038,13 @@ Cannot be used together with the
 or
 .Fl P
 option.
+.It Fl t
+Display commits in topological order.
+This option has no effect without the
+.Fl b 
+option because a linear history is sorted in topological order by definition.
+Topological sorting is disabled by default because the present implementation
+requires that commit history is fully traversed before any output can be shown.
 .It Fl x Ar commit
 Stop traversing commit history immediately after the specified
 .Ar commit
blob - 1a1732a2994a8428496e498b70ebb81e222507aa
blob + 74e2fb65d552093211aa85ccb3eaaa5d77f81f6f
--- got/got.c
+++ got/got.c
@@ -4459,7 +4459,7 @@ print_commits(struct got_object_id *root_id, struct go
     struct got_repository *repo, const char *path, int show_changed_paths,
     int show_diffstat, int show_patch, const char *search_pattern,
     int diff_context, int limit, int log_branches, int reverse_display_order,
-    struct got_reflist_object_id_map *refs_idmap, int one_line,
+    struct got_reflist_object_id_map *refs_idmap, int one_line, int toposort,
     FILE *tmpfile)
 {
 	const struct got_error *err;
@@ -4481,8 +4481,13 @@ print_commits(struct got_object_id *root_id, struct go
 	err = got_commit_graph_open(&graph, path, !log_branches);
 	if (err)
 		return err;
-	err = got_commit_graph_iter_start(graph, root_id, repo,
-	    check_cancelled, NULL);
+	if (log_branches && toposort) {
+		err = got_commit_graph_toposort(graph, root_id, repo,
+		    check_cancelled, NULL);
+	} else {
+		err = got_commit_graph_iter_start(graph, root_id, repo,
+		    check_cancelled, NULL);
+	}
 	if (err)
 		goto done;
 	for (;;) {
@@ -4610,7 +4615,7 @@ done:
 __dead static void
 usage_log(void)
 {
-	fprintf(stderr, "usage: %s log [-bdPpRs] [-C number] [-c commit] "
+	fprintf(stderr, "usage: %s log [-bdPpRst] [-C number] [-c commit] "
 	    "[-l N] [-r repository-path] [-S search-pattern] [-x commit] "
 	    "[path]\n", getprogname());
 	exit(1);
@@ -4646,6 +4651,7 @@ cmd_log(int argc, char *argv[])
 	int diff_context = -1, ch;
 	int show_changed_paths = 0, show_patch = 0, limit = 0, log_branches = 0;
 	int show_diffstat = 0, reverse_display_order = 0, one_line = 0;
+	int toposort = 0;
 	const char *errstr;
 	struct got_reflist_head refs;
 	struct got_reflist_object_id_map *refs_idmap = NULL;
@@ -4663,7 +4669,7 @@ cmd_log(int argc, char *argv[])
 
 	limit = get_default_log_limit();
 
-	while ((ch = getopt(argc, argv, "bC:c:dl:PpRr:S:sx:")) != -1) {
+	while ((ch = getopt(argc, argv, "bC:c:dl:PpRr:S:stx:")) != -1) {
 		switch (ch) {
 		case 'b':
 			log_branches = 1;
@@ -4709,6 +4715,9 @@ cmd_log(int argc, char *argv[])
 		case 's':
 			one_line = 1;
 			break;
+		case 't':
+			toposort = 1;
+			break;
 		case 'x':
 			end_commit = optarg;
 			break;
@@ -4875,7 +4884,7 @@ cmd_log(int argc, char *argv[])
 	error = print_commits(start_id, end_id, repo, path ? path : "",
 	    show_changed_paths, show_diffstat, show_patch, search_pattern,
 	    diff_context, limit, log_branches, reverse_display_order,
-	    refs_idmap, one_line, tmpfile);
+	    refs_idmap, one_line, toposort, tmpfile);
 done:
 	free(path);
 	free(repo_path);
blob - 4a83ec7819b07c9e4a689fc50177a7b979abbbf9
blob + c3e22d2178b4eebd38723079274f19c9e8b9d2d5
--- regress/cmdline/log.sh
+++ regress/cmdline/log.sh
@@ -1241,6 +1241,68 @@ test_log_commit_keywords() {
 	test_done "$testroot" "$ret"
 }
 
+test_log_toposort() {
+	local testroot=`test_init log_toposort`
+	local commit0=`git_show_head $testroot/repo`
+	local author_time0=`git_show_author_time $testroot/repo`
+
+	got checkout $testroot/repo $testroot/wt > /dev/null
+	ret=$?
+	if [ $ret -ne 0 ]; then
+		test_done "$testroot" "$ret"
+		return 1
+	fi
+
+	echo aaa > $testroot/wt/alpha
+	(cd $testroot/wt && got commit -m 'change alpha' >/dev/null)
+	local commit1=`git_show_head $testroot/repo`
+	local author_time1=`git_show_author_time $testroot/repo`
+
+	got branch -r $testroot/repo -c $commit0 newbranch
+	(cd $testroot/wt && got update -b newbranch > /dev/null)
+	echo ddd > $testroot/wt/gamma/delta
+	(cd $testroot/wt && got commit -m 'change delta' >/dev/null)
+	local commit2=`git_show_branch_head $testroot/repo newbranch`
+	local author_time2=`git_show_author_time $testroot/repo newbranch`
+
+	echo zzz > $testroot/wt/epsilon/zeta
+	(cd $testroot/wt && got commit -m 'change zeta' >/dev/null)
+	local commit3=`git_show_head $testroot/repo`
+	local author_time3=`git_show_author_time $testroot/repo newbranch`
+
+	(cd $testroot/wt && got update -b master > /dev/null)
+	(cd $testroot/wt && got merge newbranch > /dev/null)
+	local merge_commit=`git_show_head $testroot/repo`
+	local merge_time=`git_show_author_time $testroot/repo`
+
+	local short_commit0=`trim_obj_id 33 $commit0`
+	local short_commit1=`trim_obj_id 33 $commit1`
+	local short_commit2=`trim_obj_id 33 $commit2`
+	local short_commit3=`trim_obj_id 33 $commit3`
+
+	d_0=`date -u -r $author_time0 +"%G-%m-%d"`
+	d_1=`date -u -r $author_time1 +"%G-%m-%d"`
+	d_2=`date -u -r $author_time2 +"%G-%m-%d"`
+	d_3=`date -u -r $author_time3 +"%G-%m-%d"`
+	d_m=`date -u -r $merge_time +"%G-%m-%d"`
+
+	got log -r $testroot/repo -s -b -t > $testroot/stdout
+	cat > $testroot/stdout.expected <<EOF
+$d_m master  merge refs/heads/newbranch into refs/heads/master
+$d_1 $short_commit1 change alpha
+$d_3 newbranch change zeta
+$d_2 $short_commit2 change delta
+$d_0 $short_commit0 adding the test tree
+EOF
+	cmp -s $testroot/stdout.expected $testroot/stdout
+	ret=$?
+	if [ $ret -ne 0 ]; then
+		diff -u $testroot/stdout.expected $testroot/stdout
+	fi
+	test_done "$testroot" "$ret"
+}
+
+
 test_parseargs "$@"
 run_test test_log_in_repo
 run_test test_log_in_bare_repo
@@ -1259,3 +1321,4 @@ run_test test_log_merge_commit_nonexistent_path
 run_test test_log_submodule
 run_test test_log_diffstat
 run_test test_log_commit_keywords
+run_test test_log_toposort