neovim: set provider configuration to initrc

as an attempt to simplify configuration: 
instead of having wrapping arguments + an optional neovim configuration
let's always generate a neovim configuration.
The change should be transparent for most users, and require
intervention for users that fulfill both conditions:
- using remote plugins (rare already)
- that set `wrapRc = false` in wrapNeovimUnstable without loading later
  the generated luaRcContent

The fix is then to pass as wrapping arguments the wrapper's generated config via 

(wrapNeovimUnstable neovim-unwrapped { } ).overrideAttrs(oa: { wrapperArgs = oa.wrapperArgs ++ [ ''--cmd "lua dofile('${writeText "init.lua" oa.luaRcContent}')"'' ]; })

neovim: avoid creating empty newlines

doc/release-notes/rl-2605.section.md

@@ -183,6 +183,8 @@
 - `openrgb` was updated to 1.0rc2, which now uses Plugin API version 4.
   Some existing OpenRGB plugins may be incompatible or require updates.
 
+- the `neovim` wrapper sets provider-related configuration in its generated config rather than as wrapper arguments. It should not affect configuration unless you set `wrapRc` to false.
+
 - We now use the upstream wrapper script for Gradle, supporting both the `JAVA_HOME` and `GRADLE_OPTS` environment variables.
 
 ## Nixpkgs Library {#sec-nixpkgs-release-26.05-lib}

pkgs/applications/editors/neovim/wrapper.nix

@@ -104,13 +104,16 @@ let
         packpathDirs.myNeovimPackages = vimPackageInfo.vimPackage;
         finalPackdir = neovimUtils.packDir packpathDirs;
 
-        rcContent = ''
-          ${luaRcContent}
-        ''
-        + lib.optionalString (neovimRcContent' != "") ''
-          vim.cmd.source "${writeText "init.vim" neovimRcContent'}"
-        ''
-        + lib.optionalString autoconfigure (lib.concatStringsSep "\n" vimPackageInfo.pluginAdvisedLua);
+        rcContent = lib.concatStringsSep "\n" (
+          [
+            providerLuaRc
+          ]
+          ++ lib.optional (luaRcContent != "") luaRcContent
+          ++ lib.optional (neovimRcContent' != "") ''
+            vim.cmd.source "${writeText "init.vim" neovimRcContent'}"
+          ''
+          ++ lib.optionals autoconfigure vimPackageInfo.pluginAdvisedLua
+        );
 
         python3Env =
           lib.warnIf (attrs ? python3Env)
@@ -125,12 +128,7 @@ let
 
         wrapperArgsStr = if lib.isString wrapperArgs then wrapperArgs else lib.escapeShellArgs wrapperArgs;
 
-        generatedWrapperArgs = [
-          # vim accepts a limited number of commands so we join all the provider ones
-          "--add-flags"
-          ''--cmd "lua ${providerLuaRc}"''
-        ]
-        ++
+        generatedWrapperArgs =
           lib.optionals
             (
               finalAttrs.packpathDirs.myNeovimPackages.start != [ ]
@@ -181,7 +179,7 @@ let
         ++ lib.optionals finalAttrs.wrapRc [
           "--set-default"
           "VIMINIT"
-          "lua dofile('${writeText "init.lua" rcContent}')"
+          "lua dofile('${writeText "init.lua" finalAttrs.luaRcContent}')"
         ]
         ++ finalAttrs.generatedWrapperArgs;