describe --contains: default to HEAD when no commit-ish is given

diff --git a/object.c b/object.c
index 584f7acb36b68d17678b3fd6251105241794ea48..69fbbbf504d861fac42ee50bc04a49ede1f60028 100644 (file)
--- a/object.c
+++ b/object.c
@@ -43,14 +43,32 @@ int type_from_string(const char *str)
        die("invalid object type \"%s\"", str);
 }
 
+/*
+ * Return a numerical hash value between 0 and n-1 for the object with
+ * the specified sha1.  n must be a power of 2.  Please note that the
+ * return value is *not* consistent across computer architectures.
+ */
 static unsigned int hash_obj(const unsigned char *sha1, unsigned int n)
 {
        unsigned int hash;
+
+       /*
+        * Since the sha1 is essentially random, we just take the
+        * required number of bits directly from the first
+        * sizeof(unsigned int) bytes of sha1.  First we have to copy
+        * the bytes into a properly aligned integer.  If we cared
+        * about getting consistent results across architectures, we
+        * would have to call ntohl() here, too.
+        */
        memcpy(&hash, sha1, sizeof(unsigned int));
-       /* Assumes power-of-2 hash sizes in grow_object_hash */
        return hash & (n - 1);
 }
 
+/*
+ * Insert obj into the hash table hash, which has length size (which
+ * must be a power of 2).  On collisions, simply overflow to the next
+ * empty bucket.
+ */
 static void insert_obj_hash(struct object *obj, struct object **hash, unsigned int size)
 {
        unsigned int j = hash_obj(obj->sha1, size);
@@ -63,6 +81,10 @@ static void insert_obj_hash(struct object *obj, struct object **hash, unsigned i
        hash[j] = obj;
 }
 
+/*
+ * Look up the record for the given sha1 in the hash map stored in
+ * obj_hash.  Return NULL if it was not found.
+ */
 struct object *lookup_object(const unsigned char *sha1)
 {
        unsigned int i, first;
@@ -92,6 +114,11 @@ struct object *lookup_object(const unsigned char *sha1)
        return obj;
 }
 
+/*
+ * Increase the size of the hash map stored in obj_hash to the next
+ * power of 2 (but at least 32).  Copy the existing values to the new
+ * hash map.
+ */
 static void grow_object_hash(void)
 {
        int i;
@@ -114,13 +141,12 @@ static void grow_object_hash(void)
        obj_hash_size = new_hash_size;
 }
 
-void *create_object(const unsigned char *sha1, int type, void *o)
+void *create_object(const unsigned char *sha1, void *o)
 {
        struct object *obj = o;
 
        obj->parsed = 0;
        obj->used = 0;
-       obj->type = type;
        obj->flags = 0;
        hashcpy(obj->sha1, sha1);
 
@@ -132,11 +158,30 @@ void *create_object(const unsigned char *sha1, int type, void *o)
        return obj;
 }
 
+void *object_as_type(struct object *obj, enum object_type type, int quiet)
+{
+       if (obj->type == type)
+               return obj;
+       else if (obj->type == OBJ_NONE) {
+               if (type == OBJ_COMMIT)
+                       ((struct commit *)obj)->index = alloc_commit_index();
+               obj->type = type;
+               return obj;
+       }
+       else {
+               if (!quiet)
+                       error("object %s is a %s, not a %s",
+                             sha1_to_hex(obj->sha1),
+                             typename(obj->type), typename(type));
+               return NULL;
+       }
+}
+
 struct object *lookup_unknown_object(const unsigned char *sha1)
 {
        struct object *obj = lookup_object(sha1);
        if (!obj)
-               obj = create_object(sha1, OBJ_NONE, alloc_object_node());
+               obj = create_object(sha1, alloc_object_node());
        return obj;
 }
 
@@ -170,8 +215,8 @@ struct object *parse_object_buffer(const unsigned char *sha1, enum object_type t
                if (commit) {
                        if (parse_commit_buffer(commit, buffer, size))
                                return NULL;
-                       if (!commit->buffer) {
-                               commit->buffer = buffer;
+                       if (!get_cached_commit_buffer(commit, NULL)) {
+                               set_commit_buffer(commit, buffer, size);
                                *eaten_p = 1;
                        }
                        obj = &commit->object;
@@ -187,8 +232,6 @@ struct object *parse_object_buffer(const unsigned char *sha1, enum object_type t
                warning("object %s has unknown type id %d", sha1_to_hex(sha1), type);
                obj = NULL;
        }
-       if (obj && obj->type == OBJ_NONE)
-               obj->type = type;
        return obj;
 }