Do not sync direnv

It will only add the the cache to gcroots on the first computer that
built it, so everyone else has to re-fetch it.

hm/shell/direnv.nix

@@ -1,5 +1,8 @@
 # Allow switching to a specific environment when going into a directory
 {
+  config,
+  lib,
+  pkgs,
   ...
 }:
 {
@@ -11,7 +14,46 @@
         enableZshIntegration = true;
         nix-direnv.enable = true;
       };
-      git.ignores = [ ".envrc" ".direnv" ];
+      git.ignores = [
+        ".envrc"
+        ".direnv"
+      ];
+    };
+    systemd.user.services.direnv_ignore = {
+      Service = {
+        Type = "oneshot";
+        ExecStart = lib.getExe (
+          pkgs.writeShellApplication {
+            name = "direnv_ignore";
+            text =
+              ''
+                ignore_direnv() {
+                  dir="$1"
+                  if [ ! -f "$dir/.stignore" ]
+                  then
+                      touch "$dir/.stignore"
+                  fi
+                  rule="**/.direnv"
+                  if ! grep -qFx "$rule" "$dir/.stignore"
+                  then
+                      echo "$rule" >> "$dir/.stignore"
+                  fi
+                }
+              ''
+              + (lib.trivial.pipe config.frogeye.folders [
+                builtins.attrValues
+                (builtins.filter (folder: folder.syncthing.enable))
+                (builtins.map (folder: ''
+                  ignore_direnv ${lib.strings.escapeShellArg folder.fullPath}
+                ''))
+                lib.strings.concatLines
+              ]);
+          }
+        );
+      };
+      Install = {
+        WantedBy = [ "default.target" ];
+      };
     };
   };
 }