hash: provide per-algorithm null OIDs

Up until recently, object IDs did not have an algorithm member, only a
hash.  Consequently, it was possible to share one null (all-zeros)
object ID among all hash algorithms.  Now that we're going to be
handling objects from multiple hash algorithms, it's important to make
sure that all object IDs have a correct algorithm field.

Introduce a per-algorithm null OID, and add it to struct hash_algo.
Introduce a wrapper function as well, and use it everywhere we used to
use the null_oid constant.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 10 insertions, 10 deletions

diff --git a/merge-ort.c b/merge-ort.c
index 5e118a8..3e552cf 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -1291,7 +1291,7 @@ static int handle_content_merge(struct merge_options *opt,
 		two_way = ((S_IFMT & o->mode) != (S_IFMT & a->mode));
 
 		merge_status = merge_3way(opt, path,
-					  two_way ? &null_oid : &o->oid,
+					  two_way ? null_oid() : &o->oid,
 					  &a->oid, &b->oid,
 					  pathnames, extra_marker_size,
 					  &result_buf);
@@ -1313,7 +1313,7 @@ static int handle_content_merge(struct merge_options *opt,
 	} else if (S_ISGITLINK(a->mode)) {
 		int two_way = ((S_IFMT & o->mode) != (S_IFMT & a->mode));
 		clean = merge_submodule(opt, pathnames[0],
-					two_way ? &null_oid : &o->oid,
+					two_way ? null_oid() : &o->oid,
 					&a->oid, &b->oid, &result->oid);
 		if (opt->priv->call_depth && two_way && !clean) {
 			result->mode = o->mode;
@@ -2123,7 +2123,7 @@ static int process_renames(struct merge_options *opt,
 			if (type_changed) {
 				/* rename vs. typechange */
 				/* Mark the original as resolved by removal */
-				memcpy(&oldinfo->stages[0].oid, &null_oid,
+				memcpy(&oldinfo->stages[0].oid, null_oid(),
 				       sizeof(oldinfo->stages[0].oid));
 				oldinfo->stages[0].mode = 0;
 				oldinfo->filemask &= 0x06;
@@ -2762,7 +2762,7 @@ static void process_entry(struct merge_options *opt,
 			if (ci->filemask & (1 << i))
 				continue;
 			ci->stages[i].mode = 0;
-			oidcpy(&ci->stages[i].oid, &null_oid);
+			oidcpy(&ci->stages[i].oid, null_oid());
 		}
 	} else if (ci->df_conflict && ci->merged.result.mode != 0) {
 		/*
@@ -2808,7 +2808,7 @@ static void process_entry(struct merge_options *opt,
 				continue;
 			/* zero out any entries related to directories */
 			new_ci->stages[i].mode = 0;
-			oidcpy(&new_ci->stages[i].oid, &null_oid);
+			oidcpy(&new_ci->stages[i].oid, null_oid());
 		}
 
 		/*
@@ -2909,11 +2909,11 @@ static void process_entry(struct merge_options *opt,
 			new_ci->merged.result.mode = ci->stages[2].mode;
 			oidcpy(&new_ci->merged.result.oid, &ci->stages[2].oid);
 			new_ci->stages[1].mode = 0;
-			oidcpy(&new_ci->stages[1].oid, &null_oid);
+			oidcpy(&new_ci->stages[1].oid, null_oid());
 			new_ci->filemask = 5;
 			if ((S_IFMT & b_mode) != (S_IFMT & o_mode)) {
 				new_ci->stages[0].mode = 0;
-				oidcpy(&new_ci->stages[0].oid, &null_oid);
+				oidcpy(&new_ci->stages[0].oid, null_oid());
 				new_ci->filemask = 4;
 			}
 
@@ -2921,11 +2921,11 @@ static void process_entry(struct merge_options *opt,
 			ci->merged.result.mode = ci->stages[1].mode;
 			oidcpy(&ci->merged.result.oid, &ci->stages[1].oid);
 			ci->stages[2].mode = 0;
-			oidcpy(&ci->stages[2].oid, &null_oid);
+			oidcpy(&ci->stages[2].oid, null_oid());
 			ci->filemask = 3;
 			if ((S_IFMT & a_mode) != (S_IFMT & o_mode)) {
 				ci->stages[0].mode = 0;
-				oidcpy(&ci->stages[0].oid, &null_oid);
+				oidcpy(&ci->stages[0].oid, null_oid());
 				ci->filemask = 2;
 			}
 
@@ -3042,7 +3042,7 @@ static void process_entry(struct merge_options *opt,
 		/* Deleted on both sides */
 		ci->merged.is_null = 1;
 		ci->merged.result.mode = 0;
-		oidcpy(&ci->merged.result.oid, &null_oid);
+		oidcpy(&ci->merged.result.oid, null_oid());
 		ci->merged.clean = !ci->path_conflict;
 	}