fs: rename "mountpt" -> "origin" to reflect that it doesnt have to be a device

hosts/servo/fs.nix

@@ -37,7 +37,7 @@
   };
 
   sane.impermanence.stores."ext" = {
-    mountpt = "/mnt/impermanence/ext/persist";
+    origin = "/mnt/impermanence/ext/persist";
     storeDescription = "external HDD storage";
   };
   sane.fs."/mnt/impermanence/ext".mount = {};

modules/impermanence/default.nix

@@ -21,7 +21,7 @@ let
           for example, a store named "private" could have description "ecnrypted to the user's password and decrypted on login".
         '';
       };
-      mountpt = mkOption {
+      origin = mkOption {
         type = types.str;
       };
       prefix = mkOption {
@@ -163,7 +163,7 @@ in
       let
         store = opt.store;
         store-rel-path = path.from store.prefix opt.directory;
-        backing-path = path.concat [ store.mountpt store-rel-path ];
+        backing-path = path.concat [ store.origin store-rel-path ];
 
         # pass through the perm/mode overrides
         dir-acl = sane-lib.filterNonNull {

modules/impermanence/stores/crypt.nix

@@ -17,7 +17,7 @@ lib.mkIf config.sane.impermanence.enable
       stored to disk, but encrypted to an in-memory key and cleared on every boot
       so that it's unreadable after power-off
     '';
-    mountpt = store.device;
+    origin = store.device;
   };
 
 

modules/impermanence/stores/default.nix

@@ -21,7 +21,7 @@ in
     # like "/var", and then "/nix/persist/var" has different perms and something mounts funny.
     # TODO: just add assertions that sane.fs."${backing}/${dest}".dir == sane.fs."${dest}" for each mount point?
     sane.fs = lib.mapAttrs' (_name: store: {
-      name = "${store.mountpt}/home/colin";
+      name = "${store.origin}/home/colin";
       value.dir.acl = config.sane.fs."/home/colin".generated.acl;
     }) cfg.stores;
   };

modules/impermanence/stores/plaintext.nix

@@ -4,7 +4,7 @@ let
   cfg = config.sane.impermanence;
 in lib.mkIf cfg.enable {
   sane.impermanence.stores."plaintext" = {
-    mountpt = "/nix/persist";
+    origin = "/nix/persist";
   };
   # TODO: needed?
   # sane.fs."/nix".mount = {};

modules/impermanence/stores/private.nix

@@ -6,7 +6,7 @@ lib.mkIf config.sane.impermanence.enable
     storeDescription = ''
       encrypted to the user's password and auto-unlocked at login
     '';
-    mountpt = "/home/colin/private";
+    origin = "/home/colin/private";
     # files stored under here *must* have the /home/colin prefix.
     # internally, this prefix is removed so that e.g.
     # /home/colin/foo/bar when stored in `private` is visible at