Re: git-rev-list: add "--dense" flag

From

Linus Torvalds <torvalds@osdl.org>

Date

Oct 25, 2005, 18:50 UTC

Message-ID

<Pine.LNX.4.64.0510251137110.10477@g5.osdl.org>

In-Reply-To

<Pine.LNX.4.64.0510251110050.10477@g5.osdl.org>

On Tue, 25 Oct 2005, Linus Torvalds wrote:

> 
> Right now --dense will _always_ show the root commit. I didn't do the 
> logic that does the diff against an empty tree. I was lazy.
> 
> This patch does that, and may or may not work.

Never mind. It's incorrect. 

It needs to remove the parent pointers that become NULL.

This patch is even slightly tested, and might do a better job.

[ Sorry for sending untested crap out, but I have a fairly good track 
  record in general. Testing is for wimps ]

		Linus

---

diff --git a/rev-list.c b/rev-list.c
index 5f125fd..edf3b37 100644
--- a/rev-list.c
+++ b/rev-list.c
@@ -81,23 +81,28 @@ static void show_commit(struct commit *c
 	fflush(stdout);
 }
 
-static void rewrite_one(struct commit **pp)
+static int rewrite_one(struct commit **pp)
 {
 	for (;;) {
 		struct commit *p = *pp;
 		if (p->object.flags & (TREECHANGE | UNINTERESTING))
-			return;
-		/* Only single-parent commits don't have TREECHANGE */
+			return 0;
+		if (!p->parents)
+			return -1;
 		*pp = p->parents->item;
 	}
 }
 
 static void rewrite_parents(struct commit *commit)
 {
-	struct commit_list *parent = commit->parents;
-	while (parent) {
-		rewrite_one(&parent->item);
-		parent = parent->next;
+	struct commit_list **pp = &commit->parents;
+	while (*pp) {
+		struct commit_list *parent = *pp;
+		if (rewrite_one(&parent->item) < 0) {
+			*pp = parent->next;
+			continue;
+		}
+		pp = &parent->next;
 	}
 }
 
@@ -439,6 +444,30 @@ static int same_tree(struct tree *t1, st
 	return !is_different;
 }
 
+static int same_tree_as_empty(struct tree *t1)
+{
+	int retval;
+	void *tree;
+	struct tree_desc empty, real;
+
+	if (!t1)
+		return 0;
+
+	tree = read_object_with_reference(t1->object.sha1, "tree", &real.size, NULL);
+	if (!tree)
+		return 0;
+	real.buf = tree;
+
+	empty.buf = "";
+	empty.size = 0;
+
+	is_different = 0;
+	retval = diff_tree(&empty, &real, "", &diff_opt);
+	free(tree);
+
+	return retval >= 0 && !is_different;
+}
+
 static struct commit *try_to_simplify_merge(struct commit *commit, struct commit_list *parent)
 {
 	if (!commit->tree)
@@ -523,11 +552,17 @@ static void compress_list(struct commit_
 		struct commit_list *parent = commit->parents;
 		list = list->next;
 
+		if (!parent) {
+			if (!same_tree_as_empty(commit->tree))
+				commit->object.flags |= TREECHANGE;
+			continue;
+		}
+
 		/*
 		 * Exactly one parent? Check if it leaves the tree
 		 * unchanged
 		 */
-		if (parent && !parent->next) {
+		if (!parent->next) {
 			struct tree *t1 = commit->tree;
 			struct tree *t2 = parent->item->tree;
 			if (!t1 || !t2 || same_tree(t1, t2))