* mu-maildir, mu-util: error when source, target of move are the same

src/mu-maildir.c

@@ -828,7 +828,7 @@ mu_maildir_move_message (const char* oldpath, const char* targetmdir,
 	}
 
 	if (g_strcmp0 (oldpath, newfullpath) == 0) {
-		g_set_error (err, 0, MU_ERROR_FILE,
+		g_set_error (err, 0, MU_ERROR_FILE_TARGET_EQUALS_SOURCE,
 			     "target equals source");
 		return FALSE;
 	}

src/mu-util.h

@@ -441,6 +441,7 @@ enum _MuError {
 	MU_ERROR_FILE_STAT_FAILED             = 77,
 	MU_ERROR_FILE_READDIR_FAILED          = 78,
 	MU_ERROR_FILE_INVALID_SOURCE          = 79,
+	MU_ERROR_FILE_TARGET_EQUALS_SOURCE    = 80,
 	
 	/* not really an error, used in callbacks */
 	MU_STOP                               = 99,