emacs: allow wrapped emacs to execute itself again (#361145)

pkgs/applications/editors/emacs/build-support/wrapper.nix

@@ -198,6 +198,8 @@ runCommand
         --subst-var-by bash ${emacs.stdenv.shell} \
         --subst-var-by wrapperSiteLisp "$deps/share/emacs/site-lisp" \
         --subst-var-by wrapperSiteLispNative "$deps/share/emacs/native-lisp" \
+        --subst-var-by wrapperInvocationDirectory "$out/bin/" \
+        --subst-var-by wrapperInvocationName "$progname" \
         --subst-var prog
       chmod +x $out/bin/$progname
       # Create a “NOP” binary wrapper for the pure sake of it becoming a
@@ -222,6 +224,8 @@ runCommand
         --subst-var-by bash ${emacs.stdenv.shell} \
         --subst-var-by wrapperSiteLisp "$deps/share/emacs/site-lisp" \
         --subst-var-by wrapperSiteLispNative "$deps/share/emacs/native-lisp" \
+        --subst-var-by wrapperInvocationDirectory "$out/Applications/Emacs.app/Contents/MacOS/" \
+        --subst-var-by wrapperInvocationName "Emacs" \
         --subst-var-by prog "$emacs/Applications/Emacs.app/Contents/MacOS/Emacs"
       chmod +x $out/Applications/Emacs.app/Contents/MacOS/Emacs
       wrapProgramBinary $out/Applications/Emacs.app/Contents/MacOS/Emacs

pkgs/applications/editors/emacs/build-support/wrapper.sh

@@ -50,4 +50,7 @@ export emacsWithPackages_siteLisp=@wrapperSiteLisp@
 export EMACSNATIVELOADPATH="${newNativeLoadPath[*]}"
 export emacsWithPackages_siteLispNative=@wrapperSiteLispNative@
 
+export emacsWithPackages_invocationDirectory=@wrapperInvocationDirectory@
+export emacsWithPackages_invocationName=@wrapperInvocationName@
+
 exec @prog@ "$@"

pkgs/applications/editors/emacs/site-start.el

@@ -39,6 +39,16 @@ least specific (the system profile)"
       (setenv "EMACSNATIVELOADPATH" (when new-env-list
                                 (mapconcat 'identity new-env-list ":"))))))
 
+(let ((wrapper-invocation-directory (getenv "emacsWithPackages_invocationDirectory")))
+  (when wrapper-invocation-directory
+    (setq invocation-directory (file-name-as-directory wrapper-invocation-directory))
+    (setenv "emacsWithPackages_invocationDirectory" nil)))
+
+(let ((wrapper-invocation-name (getenv "emacsWithPackages_invocationName")))
+  (when wrapper-invocation-name
+    (setq invocation-name wrapper-invocation-name)
+    (setenv "emacsWithPackages_invocationName" nil)))
+
 ;;; Set up native-comp load path.
 (when (featurep 'native-compile)
   ;; Append native-comp subdirectories from `NIX_PROFILES'.