log --children

Teach git-log to support --children, which was added by f35f5603f4
to the revision machinery, and by 72276a3ecb to rev-list, but
was never added to git-log.

Signed-off-by: Jay Soffian <jaysoffian@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

log-tree.c

diff --git a/log-tree.c b/log-tree.c
index 27afcf6..98387ad 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -56,6 +56,14 @@
 	}
 }
 
+static void show_children(struct rev_info *opt, struct commit *commit, int abbrev)
+{
+	struct commit_list *p = lookup_decoration(&opt->children, &commit->object);
+	for ( ; p; p = p->next) {
+		printf(" %s", find_unique_abbrev(p->item->object.sha1, abbrev));
+	}
+}
+
 void show_decorations(struct rev_info *opt, struct commit *commit)
 {
 	const char *prefix;
@@ -303,6 +311,8 @@
 		fputs(find_unique_abbrev(commit->object.sha1, abbrev_commit), stdout);
 		if (opt->print_parents)
 			show_parents(commit, abbrev_commit);
+		if (opt->children.name)
+			show_children(opt, commit, abbrev_commit);
 		show_decorations(opt, commit);
 		if (opt->graph && !graph_is_commit_finished(opt->graph)) {
 			putchar('\n');
@@ -372,6 +382,8 @@
 		      stdout);
 		if (opt->print_parents)
 			show_parents(commit, abbrev_commit);
+		if (opt->children.name)
+			show_children(opt, commit, abbrev_commit);
 		if (parent)
 			printf(" (from %s)",
 			       find_unique_abbrev(parent->object.sha1,