From a74db82e15cd8a2c53a4a83e9a36dc7bf7a4c750 Mon Sep 17 00:00:00 2001
From: Junio C Hamano <junkio@cox.net>
Date: Sat, 19 May 2007 00:39:31 -0700
Subject: [PATCH] Teach "delta" attribute to pack-objects.

This teaches pack-objects to use .gitattributes mechanism so
that the user can specify certain blobs are not worth spending
CPU cycles to attempt deltification.

The name of the attrbute is "delta", and when it is set to
false, like this:

	== .gitattributes ==
	*.jpg	-delta

they are always stored in the plain-compressed base object
representation.

Signed-off-by: Junio C Hamano <junkio@cox.net>
---
 builtin-pack-objects.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
index 631fb8c9a6..225d311e40 100644
--- a/builtin-pack-objects.c
+++ b/builtin-pack-objects.c
@@ -1,5 +1,6 @@
 #include "builtin.h"
 #include "cache.h"
+#include "attr.h"
 #include "object.h"
 #include "blob.h"
 #include "commit.h"
@@ -40,9 +41,10 @@ struct object_entry {
 	enum object_type in_pack_type;	/* could be delta */
 	unsigned char in_pack_header_size;
 	unsigned char preferred_base; /* we do not pack this, but is available
-				       * to be used as the base objectto delta
+				       * to be used as the base object to delta
 				       * objects against.
 				       */
+	unsigned char no_try_delta;
 };
 
 /*
@@ -739,6 +741,28 @@ static unsigned name_hash(const char *name)
 	return hash;
 }
 
+static void setup_delta_attr_check(struct git_attr_check *check)
+{
+	static struct git_attr *attr_delta;
+
+	if (!attr_delta)
+		attr_delta = git_attr("delta", 5);
+
+	check[0].attr = attr_delta;
+}
+
+static int no_try_delta(const char *path)
+{
+	struct git_attr_check check[1];
+
+	setup_delta_attr_check(check);
+	if (git_checkattr(path, ARRAY_SIZE(check), check))
+		return 0;
+	if (ATTR_FALSE(check->value))
+		return 1;
+	return 0;
+}
+
 static int add_object_entry(const unsigned char *sha1, enum object_type type,
 			    const char *name, int exclude)
 {
@@ -803,6 +827,9 @@ static int add_object_entry(const unsigned char *sha1, enum object_type type,
 	if (progress)
 		display_progress(&progress_state, nr_objects);
 
+	if (name && no_try_delta(name))
+		entry->no_try_delta = 1;
+
 	return 1;
 }
 
@@ -1351,6 +1378,10 @@ static void find_deltas(struct object_entry **list, int window, int depth)
 
 		if (entry->size < 50)
 			continue;
+
+		if (entry->no_try_delta)
+			continue;
+
 		free_delta_index(n->index);
 		n->index = NULL;
 		free(n->data);
@@ -1378,6 +1409,8 @@ static void find_deltas(struct object_entry **list, int window, int depth)
 			m = array + other_idx;
 			if (!m->entry)
 				break;
+			if (m->entry->no_try_delta)
+				continue;
 			if (try_delta(n, m, max_depth) < 0)
 				break;
 		}
-- 
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