environment: move object database functions into object layer

The `odb_mkstemp()` and `odb_pack_keep()` functions are quite clearly
tied to the object store, but regardless of that they are located in
"environment.c". Move them over, which also helps to get rid of
dependencies on `the_repository` in the environment subsystem.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

object-file.c

@@ -419,6 +419,39 @@ enum scld_error safe_create_leading_directories_const(const char *path)
 	return result;
 }
 
+int odb_mkstemp(struct strbuf *temp_filename, const char *pattern)
+{
+	int fd;
+	/*
+	 * we let the umask do its job, don't try to be more
+	 * restrictive except to remove write permission.
+	 */
+	int mode = 0444;
+	git_path_buf(temp_filename, "objects/%s", pattern);
+	fd = git_mkstemp_mode(temp_filename->buf, mode);
+	if (0 <= fd)
+		return fd;
+
+	/* slow path */
+	/* some mkstemp implementations erase temp_filename on failure */
+	git_path_buf(temp_filename, "objects/%s", pattern);
+	safe_create_leading_directories(temp_filename->buf);
+	return xmkstemp_mode(temp_filename->buf, mode);
+}
+
+int odb_pack_keep(const char *name)
+{
+	int fd;
+
+	fd = open(name, O_RDWR|O_CREAT|O_EXCL, 0600);
+	if (0 <= fd)
+		return fd;
+
+	/* slow path */
+	safe_create_leading_directories_const(name);
+	return open(name, O_RDWR|O_CREAT|O_EXCL, 0600);
+}
+
 static void fill_loose_path(struct strbuf *buf, const struct object_id *oid)
 {
 	int i;