nix-profile{,-daemon}.fish: Do not source twice

In order for the script not be sourced multiple times by the same shell
instance, `__ETC_PROFILE_NIX_SOURCED` needs to be set with a `--global`
flag.

Both files are almost identical.  And style differences make it harder
to see what is actually different and keep them in sync, when it is
required.

scripts/nix-profile-daemon.fish.in

@@ -1,3 +1,13 @@
+# Only execute this file once per shell.
+if test -z "$HOME" || \
+    test -n "$__ETC_PROFILE_NIX_SOURCED"
+    exit
+end
+
+set --global __ETC_PROFILE_NIX_SOURCED 1
+
+# Local helpers
+
 function add_path --argument-names new_path
     if type -q fish_add_path
         # fish 3.2.0 or newer
@@ -10,13 +20,7 @@ function add_path --argument-names new_path
     end
 end
 
-# Only execute this file once per shell.
+# Main configuration
-if test -n "$__ETC_PROFILE_NIX_SOURCED"
-    exit
-end
-
-set __ETC_PROFILE_NIX_SOURCED 1
-
 set --export NIX_PROFILES "@localstatedir@/nix/profiles/default $HOME/.nix-profile"
 
 # Populate bash completions, .desktop files, etc
@@ -54,4 +58,6 @@ end
 add_path "@localstatedir@/nix/profiles/default/bin"
 add_path "$HOME/.nix-profile/bin"
 
+# Cleanup
+
 functions -e add_path

scripts/nix-profile.fish.in

@@ -1,3 +1,13 @@
+# Only execute this file once per shell.
+if test -z "$HOME" || test -z "$USER" || \
+    test -n "$__ETC_PROFILE_NIX_SOURCED"
+    exit
+end
+
+set --global __ETC_PROFILE_NIX_SOURCED 1
+
+# Local helpers
+
 function add_path --argument-names new_path
     if type -q fish_add_path
         # fish 3.2.0 or newer
@@ -10,7 +20,7 @@ function add_path --argument-names new_path
     end
 end
 
-if test -n "$HOME" && test -n "$USER"
+# Main configuration
 
 # Set up the per-user profile.
 
@@ -54,6 +64,7 @@ if test -n "$HOME" && test -n "$USER"
 
 add_path "$NIX_LINK/bin"
 set --erase NIX_LINK
-end
+
+# Cleanup
 
 functions -e add_path