pack-write: pass hash_algo to write_rev_file()

The `write_rev_file()` function uses the global `the_hash_algo` variable
to access the repository's hash_algo. To avoid global variable usage,
pass a hash_algo from the layers above. Also modify children functions
`write_rev_file_order()` and `write_rev_header()` to accept
'the_hash_algo'.

Altough the layers above could have access to the hash_algo internally,
simply pass in `the_hash_algo`. This avoids any compatibility issues and
bubbles up global variable usage to upper layers which can be eventually
resolved.

However, in `midx-write.c`, since all usage of global variables is
removed, don't reintroduce them and instead use the `repo` available in
the context.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/index-pack.c

@@ -2096,9 +2096,9 @@ int cmd_index_pack(int argc,
 	curr_index = write_idx_file(the_hash_algo, index_name, idx_objects,
 				    nr_objects, &opts, pack_hash);
 	if (rev_index)
-		curr_rev_index = write_rev_file(rev_index_name, idx_objects,
-						nr_objects, pack_hash,
-						opts.flags);
+		curr_rev_index = write_rev_file(the_hash_algo, rev_index_name,
+						idx_objects, nr_objects,
+						pack_hash, opts.flags);
 	free(idx_objects);
 
 	if (!verify)

midx-write.c

@@ -658,8 +658,8 @@ static void write_midx_reverse_index(char *midx_name, unsigned char *midx_hash,
 	strbuf_addf(&buf, "%s-%s.rev", midx_name, hash_to_hex_algop(midx_hash,
 								    ctx->repo->hash_algo));
 
-	tmp_file = write_rev_file_order(NULL, ctx->pack_order, ctx->entries_nr,
-					midx_hash, WRITE_REV);
+	tmp_file = write_rev_file_order(ctx->repo->hash_algo, NULL, ctx->pack_order,
+					ctx->entries_nr, midx_hash, WRITE_REV);
 
 	if (finalize_object_file(tmp_file, buf.buf))
 		die(_("cannot store reverse index file"));

pack-write.c

@@ -194,11 +194,12 @@ static int pack_order_cmp(const void *va, const void *vb, void *ctx)
 	return 0;
 }
 
-static void write_rev_header(struct hashfile *f)
+static void write_rev_header(const struct git_hash_algo *hash_algo,
+			     struct hashfile *f)
 {
 	hashwrite_be32(f, RIDX_SIGNATURE);
 	hashwrite_be32(f, RIDX_VERSION);
-	hashwrite_be32(f, oid_version(the_hash_algo));
+	hashwrite_be32(f, oid_version(hash_algo));
 }
 
 static void write_rev_index_positions(struct hashfile *f,
@@ -215,7 +216,8 @@ static void write_rev_trailer(struct hashfile *f, const unsigned char *hash)
 	hashwrite(f, hash, the_hash_algo->rawsz);
 }
 
-char *write_rev_file(const char *rev_name,
+char *write_rev_file(const struct git_hash_algo *hash_algo,
+		     const char *rev_name,
 		     struct pack_idx_entry **objects,
 		     uint32_t nr_objects,
 		     const unsigned char *hash,
@@ -233,15 +235,16 @@ char *write_rev_file(const char *rev_name,
 		pack_order[i] = i;
 	QSORT_S(pack_order, nr_objects, pack_order_cmp, objects);
 
-	ret = write_rev_file_order(rev_name, pack_order, nr_objects, hash,
-				   flags);
+	ret = write_rev_file_order(hash_algo, rev_name, pack_order, nr_objects,
+				   hash, flags);
 
 	free(pack_order);
 
 	return ret;
 }
 
-char *write_rev_file_order(const char *rev_name,
+char *write_rev_file_order(const struct git_hash_algo *hash_algo,
+			   const char *rev_name,
 			   uint32_t *pack_order,
 			   uint32_t nr_objects,
 			   const unsigned char *hash,
@@ -280,7 +283,7 @@ char *write_rev_file_order(const char *rev_name,
 		return NULL;
 	}
 
-	write_rev_header(f);
+	write_rev_header(hash_algo, f);
 
 	write_rev_index_positions(f, pack_order, nr_objects);
 	write_rev_trailer(f, hash);
@@ -568,8 +571,8 @@ void stage_tmp_packfiles(const struct git_hash_algo *hash_algo,
 	if (adjust_shared_perm(*idx_tmp_name))
 		die_errno("unable to make temporary index file readable");
 
-	rev_tmp_name = write_rev_file(NULL, written_list, nr_written, hash,
-				      pack_idx_opts->flags);
+	rev_tmp_name = write_rev_file(hash_algo, NULL, written_list, nr_written,
+				      hash, pack_idx_opts->flags);
 
 	if (pack_idx_opts->flags & WRITE_MTIMES) {
 		mtimes_tmp_name = write_mtimes_file(to_pack, written_list,

pack.h

@@ -105,8 +105,18 @@ struct ref;
 
 void write_promisor_file(const char *promisor_name, struct ref **sought, int nr_sought);
 
-char *write_rev_file(const char *rev_name, struct pack_idx_entry **objects, uint32_t nr_objects, const unsigned char *hash, unsigned flags);
-char *write_rev_file_order(const char *rev_name, uint32_t *pack_order, uint32_t nr_objects, const unsigned char *hash, unsigned flags);
+char *write_rev_file(const struct git_hash_algo *hash_algo,
+		     const char *rev_name,
+		     struct pack_idx_entry **objects,
+		     uint32_t nr_objects,
+		     const unsigned char *hash,
+		     unsigned flags);
+char *write_rev_file_order(const struct git_hash_algo *hash_algo,
+			   const char *rev_name,
+			   uint32_t *pack_order,
+			   uint32_t nr_objects,
+			   const unsigned char *hash,
+			   unsigned flags);
 
 /*
  * The "hdr" output buffer should be at least this big, which will handle sizes