Re: [PATCH 2/5] support fetching into a shallow repository

A shallow commit is a commit which has parents, which in turn are
"grafted away", i.e. the commit appears as if it were a root.

Since these shallow commits should not be edited by the user, but
only by core git, they are recorded in the file $GIT_DIR/shallow.

A repository containing shallow commits is called shallow.

The advantage of a shallow repository is that even if the upstream
contains lots of history, your local (shallow) repository needs not
occupy much disk space.

The disadvantage is that you might miss a merge base when pulling
some remote branch.

Signed-off-by: Johannes Schindelin <redacted>
---

diff --git a/shallow.c b/shallow.c
new file mode 100644
index 0000000..3cf2127
--- /dev/null
+++ b/shallow.c

...
+struct commit_list *get_shallow_commits(struct object_array *heads, int depth)
+{
+	int i = 0, cur_depth = 0;
+	struct commit_list *result = NULL;
+	struct object_array stack = {0, 0, NULL};
+	struct commit *commit = NULL;
+
+	while (commit || i < heads->nr || stack.nr) {
+		struct commit_list *p;
+		if (!commit) {
...
+		}
+		parse_commit(commit);
+		cur_depth++;
+		for (p = commit->parents, commit = NULL; p; p = p->next) {
+			if (!p->item->util) {
...
+			} else {
...
+			}
+			if (cur_depth < depth) {
+				if (p->next)
+					add_object_array(&p->item->object,
+							NULL, &stack);
+				else {
+					commit = p->item;
+					cur_depth = *(int *)commit->util;
+				}
+			} else
+				commit_list_insert(p->item, &result);
+		}
+	}
+
+	return result;
+}