Tmpfiles: allow minus sign for letter types

Allow the minus sign at the end of a type specification, indicating that
a failure in executing that line is ignored.

lenses/tests/test_tmpfiles.aug

@@ -79,6 +79,24 @@ Tree for <exclamation_mark> *)
         { "argument" = "-" }
     }
 
+  (* Variable: minus
+Example with an minus mark in the type *)
+  let minus = "D- /tmp/foo - - - - -\n"
+
+  (* Variable: minus_tree
+Tree for <minus_tree> *)
+  let minus_tree =
+    {
+        "1"
+        { "type" = "D-" }
+        { "path" = "/tmp/foo" }
+        { "mode" = "-" }
+        { "uid" = "-" }
+        { "gid" = "-" }
+        { "age" = "-" }
+        { "argument" = "-" }
+    }
+
   (* Variable: short
 Example with only type and path *)
   let short = "A+ /tmp/foo\n"
@@ -357,6 +375,8 @@ Invalid example that contain invalid mode (letter) *)
 
   test Tmpfiles.lns get exclamation_mark = exclamation_mark_tree
 
+  test Tmpfiles.lns get minus = minus_tree
+
   test Tmpfiles.lns get short = short_tree
 
   test Tmpfiles.lns get short_mode = short_mode_tree

lenses/tmpfiles.aug

@@ -49,11 +49,12 @@ Empty lines *)
 (* Group: Lense-specific primitives *)
 
   (* View: type
-One letter. Some of them can have a "+" and all can have a "!".
+One letter. Some of them can have a "+" and all can have an
+exclamation mark ("!") and/or minus sign ("-").
 
 Not all letters are valid.
 *)
-  let type     = /([fFwdDevqQpLcbCxXrRzZtThHaAm]|[fFwpLcbaA]\+)!?/
+  let type     = /([fFwdDevqQpLcbCxXrRzZtThHaAm]|[fFwpLcbaA]\+)!?-?/
 
   (* View: mode
 "-", or 3-4 bytes. Optionally starts with a "~". *)