syncthing: use service files from upstream

Currently only for the user services as NixOS handles the named system
instances slightly differently.

syncthing and syncthing-inotify are done the same way.

There are 4 parts to this:

 1) Copy in the upstream unit files
 2) Make the nixos module use the definition from upstream
 3) Enable restarting of all instances (system and user) on resume
 4) Allow the traffic in the firewall on default ports if wanted

fixes #18973

pkgs/applications/networking/syncthing/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchFromGitHub, go }:
+{ stdenv, lib, fetchFromGitHub, go, pkgs }:
 
 stdenv.mkDerivation rec {
   version = "0.14.8";
@@ -25,11 +25,24 @@ stdenv.mkDerivation rec {
   '';
 
   installPhase = ''
-    mkdir -p $out/bin
+    mkdir -p $out/bin $out/etc/systemd/{system,user}
+
     cp bin/* $out/bin
+  '' + lib.optionalString (stdenv.isLinux) ''
+    substitute etc/linux-systemd/system/syncthing-resume.service \
+               $out/etc/systemd/system/syncthing-resume.service \
+               --replace /usr/bin/pkill ${pkgs.procps}/bin/pkill
+
+    substitute etc/linux-systemd/system/syncthing@.service \
+               $out/etc/systemd/system/syncthing@.service \
+               --replace /usr/bin/syncthing $out/bin/syncthing
+
+    substitute etc/linux-systemd/user/syncthing.service \
+               $out/etc/systemd/user/syncthing.service \
+               --replace /usr/bin/syncthing $out/bin/syncthing
   '';
 
-  meta = {
+  meta = with stdenv.lib; {
     homepage = https://www.syncthing.net/;
     description = "Open Source Continuous File Synchronization";
     license = stdenv.lib.licenses.mpl20;

pkgs/applications/networking/syncthing/inotify.nix

@@ -15,12 +15,23 @@ buildGoPackage rec {
 
   goDeps = ./inotify-deps.nix;
 
-  meta = {
+  postInstall = ''
+    mkdir -p $bin/etc/systemd/{system,user}
+
+    substitute $src/etc/linux-systemd/system/syncthing-inotify@.service \
+               $bin/etc/systemd/system/syncthing-inotify@.service \
+               --replace /usr/bin/syncthing-inotify $bin/bin/syncthing-inotify
+
+    substitute $src/etc/linux-systemd/user/syncthing-inotify.service \
+               $bin/etc/systemd/user/syncthing-inotify.service \
+               --replace /usr/bin/syncthing-inotify $bin/bin/syncthing-inotify
+  '';
+
+  meta = with stdenv.lib; {
     homepage = https://github.com/syncthing/syncthing-inotify;
     description = "File watcher intended for use with Syncthing";
-    license = stdenv.lib.licenses.mpl20;
-    maintainers = with stdenv.lib.maintainers; [ joko ];
-    platforms = with stdenv.lib.platforms; linux ++ freebsd ++ openbsd ++ netbsd;
+    license = licenses.mpl20;
+    maintainers = with maintainers; [ joko peterhoeg ];
+    platforms = platforms.unix;
   };
-
 }