Revert some changes

Author: Shay Bergmann

nix/pkgs/mantis/default.nix

@@ -12,10 +12,9 @@
           filter = path: _: !lib.hasSuffix "nix" path;
         };
     in
-    if lib.isStorePath src then src
-    else if isGit then
-      if dirty then mkSrc (gitignoreSource src) else repo
-    else filterSrc src;
+    if isGit then
+      if dirty then filterSrc (gitignoreSource src) else repo
+    else src;
 
   mantis-source = mkSrc src;