Add direnv config

programs/direnv.nix

@@ -7,7 +7,7 @@
     nix-direnv.enable = true;
   };
   
-  home.sessionVariables = {
+  home.file.".config/direnv/direnvrc" = {
-    DIRENV_CACHE = "${config.home.homeDirectory}/.cache/direnv";
+    source = ./direnv/direnvrc;
   };
 }

programs/direnv/direnvrc

@@ -0,0 +1,15 @@
+# Place in ~/.config/direnv/direnvrc
+
+# Two things to know:
+# * `direnv_layour_dir` is called once for every {.direnvrc,.envrc} sourced
+# * The indicator for a different direnv file being sourced is a different $PWD value
+# This means we can hash $PWD to get a fully unique cache path for any given environment
+
+: ${XDG_CACHE_HOME:=$HOME/.cache}
+declare -A direnv_layout_dirs
+direnv_layout_dir() {
+	echo "${direnv_layout_dirs[$PWD]:=$(
+		echo -n "$XDG_CACHE_HOME"/direnv/layouts/
+		echo -n "$PWD" | sha1sum | cut -d ' ' -f 1
+	)}"
+}