sha1_file_name(): overwrite buffer instead of appending

The sha1_file_name() function is used to generate the path to a loose
object in the object directory. It doesn't make much sense for it to
append, since the the path we write may be absolute (i.e., you cannot
reliably build up a path with it). Because many callers use it with a
static buffer, they have to strbuf_reset() manually before each call
(and the other callers always use an empty buffer, so they don't care
either way). Let's handle this automatically.

Since we're changing the semantics, let's take the opportunity to give
it a more hash-neutral name (which will also catch any callers from
topics in flight).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

http-walker.c

@@ -547,7 +547,7 @@ static int fetch_object(struct walker *walker, unsigned char *sha1)
 		ret = error("File %s has bad hash", hex);
 	} else if (req->rename < 0) {
 		struct strbuf buf = STRBUF_INIT;
-		sha1_file_name(the_repository, &buf, req->sha1);
+		loose_object_path(the_repository, &buf, req->sha1);
 		ret = error("unable to write sha1 filename %s", buf.buf);
 		strbuf_release(&buf);
 	}

http.c

@@ -2314,7 +2314,7 @@ struct http_object_request *new_http_object_request(const char *base_url,
 	hashcpy(freq->sha1, sha1);
 	freq->localfile = -1;
 
-	sha1_file_name(the_repository, &filename, sha1);
+	loose_object_path(the_repository, &filename, sha1);
 	strbuf_addf(&freq->tmpfile, "%s.temp", filename.buf);
 
 	strbuf_addf(&prevfile, "%s.prev", filename.buf);
@@ -2465,7 +2465,7 @@ int finish_http_object_request(struct http_object_request *freq)
 		unlink_or_warn(freq->tmpfile.buf);
 		return -1;
 	}
-	sha1_file_name(the_repository, &filename, freq->sha1);
+	loose_object_path(the_repository, &filename, freq->sha1);
 	freq->rename = finalize_object_file(freq->tmpfile.buf, filename.buf);
 	strbuf_release(&filename);
 

object-store.h

@@ -157,7 +157,7 @@ void raw_object_store_clear(struct raw_object_store *o);
  * Put in `buf` the name of the file in the local object database that
  * would be used to store a loose object with the specified sha1.
  */
-void sha1_file_name(struct repository *r, struct strbuf *buf, const unsigned char *sha1);
+void loose_object_path(struct repository *r, struct strbuf *buf, const unsigned char *sha1);
 
 void *map_sha1_file(struct repository *r, const unsigned char *sha1, unsigned long *size);
 

sha1-file.c

@@ -346,8 +346,10 @@ static void fill_sha1_path(struct strbuf *buf, const unsigned char *sha1)
 	}
 }
 
-void sha1_file_name(struct repository *r, struct strbuf *buf, const unsigned char *sha1)
+void loose_object_path(struct repository *r, struct strbuf *buf,
+		       const unsigned char *sha1)
 {
+	strbuf_reset(buf);
 	strbuf_addstr(buf, r->objects->objectdir);
 	strbuf_addch(buf, '/');
 	fill_sha1_path(buf, sha1);
@@ -735,8 +737,7 @@ static int check_and_freshen_local(const struct object_id *oid, int freshen)
 {
 	static struct strbuf buf = STRBUF_INIT;
 
-	strbuf_reset(&buf);
-	sha1_file_name(the_repository, &buf, oid->hash);
+	loose_object_path(the_repository, &buf, oid->hash);
 
 	return check_and_freshen_file(buf.buf, freshen);
 }
@@ -888,16 +889,15 @@ int git_open_cloexec(const char *name, int flags)
  *
  * The "path" out-parameter will give the path of the object we found (if any).
  * Note that it may point to static storage and is only valid until another
- * call to sha1_file_name(), etc.
+ * call to loose_object_path(), etc.
  */
 static int stat_sha1_file(struct repository *r, const unsigned char *sha1,
 			  struct stat *st, const char **path)
 {
 	struct object_directory *odb;
 	static struct strbuf buf = STRBUF_INIT;
 
-	strbuf_reset(&buf);
-	sha1_file_name(r, &buf, sha1);
+	loose_object_path(r, &buf, sha1);
 	*path = buf.buf;
 
 	if (!lstat(*path, st))
@@ -926,8 +926,7 @@ static int open_sha1_file(struct repository *r,
 	int most_interesting_errno;
 	static struct strbuf buf = STRBUF_INIT;
 
-	strbuf_reset(&buf);
-	sha1_file_name(r, &buf, sha1);
+	loose_object_path(r, &buf, sha1);
 	*path = buf.buf;
 
 	fd = git_open(*path);
@@ -1626,8 +1625,7 @@ static int write_loose_object(const struct object_id *oid, char *hdr,
 	static struct strbuf tmp_file = STRBUF_INIT;
 	static struct strbuf filename = STRBUF_INIT;
 
-	strbuf_reset(&filename);
-	sha1_file_name(the_repository, &filename, oid->hash);
+	loose_object_path(the_repository, &filename, oid->hash);
 
 	fd = create_tmpfile(&tmp_file, filename.buf);
 	if (fd < 0) {