fs: allow specifying text for a symlink directly

modules/fs/default.nix

@@ -21,7 +21,7 @@ let
         default = null;
       };
       symlink = mkOption {
-        type = types.nullOr symlinkEntry;
+        type = types.nullOr (symlinkEntryFor name);
         default = null;
       };
       generated = mkOption {
@@ -111,15 +111,25 @@ let
   # takes no special options
   dirEntry = types.submodule propagatedGenerateMod;
 
-  symlinkEntry = types.submodule {
+  symlinkEntryFor = path: types.submodule ({ config, ...}: {
     options = {
       inherit (propagatedGenerateMod.options) acl;
       target = mkOption {
-        type = types.str;
+        type = types.coercedTo types.package toString types.str;
         description = "fs path to link to";
       };
+      text = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = "create a file in the /nix/store with the provided text and use that as the target";
+      };
     };
-  };
+    config = {
+      target = lib.mkIf (config.text != null) (
+        pkgs.writeText (path-lib.leaf path) config.text
+      );
+    };
+  });
 
   generatedEntry = types.submodule {
     options = {

modules/home-manager/ssh.nix

@@ -6,14 +6,14 @@ let
   known_hosts_text = builtins.concatStringsSep
     "\n"
     (builtins.attrValues (import ../pubkeys.nix).hosts);
-  mkSymlink = target: {
-    symlink.target = target;
+  mkSymlink = text: {
+    symlink.text = text;
     wantedBeforeBy = [ "multi-user.target" ];
   };
 in lib.mkIf config.sane.home-manager.enable {
   # ssh key is stored in private storage
   sane.persist.home.private = [ ".ssh/id_ed25519" ];
-  sane.fs."/home/colin/.ssh/id_ed25519.pub" = mkSymlink (builtins.toString (pkgs.writeText "id_ed25519.pub" user_pubkey));
+  sane.fs."/home/colin/.ssh/id_ed25519.pub" = mkSymlink user_pubkey;
 
   home-manager.users.colin = {
     programs.ssh.enable = true;

modules/lib/path.nix

@@ -1,6 +1,7 @@
 { lib, utils, ... }:
 
 let path = rec {
+
   # split the string path into a list of string components.
   # root directory "/" becomes the empty list [].
   # implicitly performs normalization so that:
@@ -19,6 +20,10 @@ let path = rec {
   hasParent = str: (path.parent str) != (path.norm str);
   # return the path from `from` to `to`, but keeping absolute form
   # e.g. `pathFrom "/home/colin" "/home/colin/foo/bar"` -> "/foo/bar"
+
+  # return the last path component; error on the empty path
+  leaf = str: lib.last (split str);
+
   from = start: end: let
     s = path.norm start;
     e = path.norm end;