Re: [PATCH] add--interactive: handle initial commit better

[Jeff King <peff@peff.net>]

On Wed, Feb 13, 2008 at 05:50:51AM -0500, Jeff King wrote:

> And here it is. I think this is a more sane approach in general than the
> last patch. The only ugly thing is the empty tree hack, but that can be
> addressed with a patch to allow referencing the empty tree without it
> existing in the object db.

And this patch hard-codes the empty tree. I _think_ this shouldn't cause
us any problems, as it just reuses the existing pretend_sha1_file
infrastructure. However that infrastructure is very rarely used.

This patch also contains the matching fix to git-add--interactive (on
top of my last patch). They should probably just be squashed together,
but I can submit a cleaned up 2-patch series if people agree that this
is a good idea.

-- >8 --
hard-code the empty tree object

Now any commands may reference the empty tree object by its
sha1 (4b825dc642cb6eb9a060e54bf8d69288fbee4904). This is
useful for showing some diffs, especially for initial
commits.

Signed-off-by: Jeff King <peff@peff.net>
---
 git-add--interactive.perl |   13 ++-----------
 sha1_file.c               |   11 +++++++++++
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/git-add--interactive.perl b/git-add--interactive.perl
index bae631e..a0a81f1 100755
--- a/git-add--interactive.perl
+++ b/git-add--interactive.perl
@@ -91,17 +91,8 @@ my $status_head = sprintf($status_fmt, 'staged', 'unstaged', 'path');
 	}
 }
 
-{
-	my $sha1;
-	sub get_empty_tree {
-		if (!$sha1) {
-			local $ENV{GIT_INDEX_FILE} = "$GIT_DIR/empty_index";
-			$sha1 = run_cmd_pipe(qw(git write-tree));
-			chomp $sha1;
-			unlink($ENV{GIT_INDEX_FILE});
-		}
-		return $sha1;
-	}
+sub get_empty_tree {
+	return '4b825dc642cb6eb9a060e54bf8d69288fbee4904';
 }
 
 # Returns list of hashes, contents of each of which are:
diff --git a/sha1_file.c b/sha1_file.c
index 4179949..1a6c7c8 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -1845,6 +1845,15 @@ static struct cached_object {
 } *cached_objects;
 static int cached_object_nr, cached_object_alloc;
 
+static struct cached_object empty_tree = {
+	/* empty tree sha1: 4b825dc642cb6eb9a060e54bf8d69288fbee4904 */
+	"\x4b\x82\x5d\xc6\x42\xcb\x6e\xb9\xa0\x60"
+	"\xe5\x4b\xf8\xd6\x92\x88\xfb\xee\x49\x04",
+	OBJ_TREE,
+	"",
+	0
+};
+
 static struct cached_object *find_cached_object(const unsigned char *sha1)
 {
 	int i;
@@ -1854,6 +1863,8 @@ static struct cached_object *find_cached_object(const unsigned char *sha1)
 		if (!hashcmp(co->sha1, sha1))
 			return co;
 	}
+	if (!hashcmp(sha1, empty_tree.sha1))
+		return &empty_tree;
 	return NULL;
 }
 
-- 
1.5.4.1.1297.g3482b-dirty