Use hashcpy() when copying object names

We invented hashcpy() to keep the abstraction of "object name"
behind it.  Use it instead of calling memcpy() with hard-coded
20-byte length when moving object names between pieces of memory.

Leave ppc/sha1.c as-is, because the function is about the SHA-1 hash
algorithm whose output is and will always be 20 bytes.

Helped-by: Michael Haggerty <mhagger@alum.mit.edu>
Helped-by: Duy Nguyen <pclouds@gmail.com>
Signed-off-by: Sun He <sunheehnus@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

bundle.c

@@ -19,7 +19,7 @@ static void add_to_ref_list(const unsigned char *sha1, const char *name,
 		list->list = xrealloc(list->list,
 				list->alloc * sizeof(list->list[0]));
 	}
-	memcpy(list->list[list->nr].sha1, sha1, 20);
+	hashcpy(list->list[list->nr].sha1, sha1);
 	list->list[list->nr].name = xstrdup(name);
 	list->nr++;
 }

grep.c

@@ -1650,7 +1650,7 @@ void grep_source_init(struct grep_source *gs, enum grep_source_type type,
 		break;
 	case GREP_SOURCE_SHA1:
 		gs->identifier = xmalloc(20);
-		memcpy(gs->identifier, identifier, 20);
+		hashcpy(gs->identifier, identifier);
 		break;
 	case GREP_SOURCE_BUF:
 		gs->identifier = NULL;

pack-bitmap-write.c

@@ -530,7 +530,7 @@ void bitmap_writer_finish(struct pack_idx_entry **index,
 	header.version = htons(default_version);
 	header.options = htons(flags | options);
 	header.entry_count = htonl(writer.selected_nr);
-	memcpy(header.checksum, writer.pack_checksum, 20);
+	hashcpy(header.checksum, writer.pack_checksum);
 
 	sha1write(f, &header, sizeof(header));
 	dump_bitmap(f, writer.commits);

reflog-walk.c

@@ -32,8 +32,8 @@ static int read_one_reflog(unsigned char *osha1, unsigned char *nsha1,
 			sizeof(struct reflog_info));
 	}
 	item = array->items + array->nr;
-	memcpy(item->osha1, osha1, 20);
-	memcpy(item->nsha1, nsha1, 20);
+	hashcpy(item->osha1, osha1);
+	hashcpy(item->nsha1, nsha1);
 	item->email = xstrdup(email);
 	item->timestamp = timestamp;
 	item->tz = tz;

refs.c

@@ -1222,7 +1222,7 @@ static int resolve_gitlink_packed_ref(struct ref_cache *refs,
 	if (ref == NULL)
 		return -1;
 
-	memcpy(sha1, ref->u.value.sha1, 20);
+	hashcpy(sha1, ref->u.value.sha1);
 	return 0;
 }