Re: git-rev-list: add "--dense" flag
From: Linus Torvalds <torvalds@osdl.org>
Date: 2016-06-15 22:42:09
Subsystem:
the rest · Maintainer:
Linus Torvalds
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's -close- to being correct, but it will SIGSEGV because now the root won't necessarily have the TREECHANGED flag, so now it can follow the root down to its parents (which is a NULL pointer - that's the definition of a root commit, of course). 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))