mkarchiso: write grubenv in _make_common_bootmode_grub_cfg

Add all variables that we replace with values in configuration files.

Keep `${isofs_dir}/${install_dir}/grubenv` with fewer variables for
backwards compatibility. It will be removed in the future.

CHANGELOG.rst

@@ -24,6 +24,9 @@ Changed
   the ISO volume and load the ``grub.cfg`` from there.
 - Moved GRUB files on ISO 9660 from ``/EFI/BOOT/`` to a boot-platform neutral place ``/boot/grub/``. This does not apply
   to the EFI binaries that remain in the default/fallback boot path.
+- Move ``grubenv`` to ``/boot/grub/grubenv`` on ISO 9660 so that it is together with the rest of GRUB-specific files.
+  Additionally write more variables in it. The previous ``/${install_dir}/grubenv`` (``/arch/grubenv`` for releng)
+  is deprecated and a future archiso release will not create this file anymore.
 
 Removed
 -------

README.rst

@@ -129,7 +129,7 @@ boot the iso image from GRUB with a version specific cow directory to mitigate o
 .. code:: sh
 
    loopback loop archlinux.iso
-   load_env -f (loop)/arch/grubenv
+   load_env -f (loop)/boot/grub/grubenv
    linux (loop)/arch/boot/x86_64/vmlinuz-linux ... \
        cow_directory=${NAME}/${VERSION} ...
    initrd (loop)/arch/boot/x86_64/initramfs-linux-lts.img

archiso/mkarchiso

@@ -618,6 +618,18 @@ fi
 EOF
     grubembedcfg="${grubembedcfg//'%UUID_SEARCH_FILENAME%'/"${uuid_search_filename}"}"
     printf '%s\n' "$grubembedcfg" > "${work_dir}/grub-embed.cfg"
+
+    # Write grubenv
+    printf '%.1024s' \
+        "$(printf '# GRUB Environment Block\nNAME=%s\nVERSION=%s\nARCHISO_LABEL=%s\nINSTALL_DIR=%s\nARCH=%s\nUUID_SEARCH_FILENAME=%s\n%s' \
+            "${iso_name}" \
+            "${iso_version}" \
+            "${iso_label}" \
+            "${install_dir}" \
+            "${arch}" \
+            "${uuid_search_filename}" \
+            "$(printf '%0.1s' "#"{1..1024})")" \
+        > "${work_dir}/grub/grubenv"
 }
 
 _make_bootmode_uefi-ia32.grub.esp() {
@@ -1067,6 +1079,10 @@ _export_netboot_artifacts() {
     _msg_info "Exporting netboot artifacts..."
     install -d -m 0755 "${out_dir}"
     cp -a -- "${isofs_dir}/${install_dir}/" "${out_dir}/"
+
+    # Remove grubenv since it serves no purpose in netboot artifacts
+    rm -f -- "${out_dir}/${install_dir}/grubenv"
+
     _msg_info "Done!"
     du -hs -- "${out_dir}/${install_dir}"
 }
@@ -1663,7 +1679,13 @@ _make_version() {
         install -d -m 0755 -- "${isofs_dir}/${install_dir}"
         # Write version file to ISO 9660
         printf '%s\n' "${iso_version}" > "${isofs_dir}/${install_dir}/version"
+
+    fi
+    if [[ "${buildmode}" == "iso" ]]; then
         # Write grubenv with version information to ISO 9660
+        # TODO: after sufficient time has passed, do not create this file anymore when GRUB boot modes are used.
+        #       _make_common_bootmode_grub_cfg already creates ${isofs_dir}/boot/grub/grubenv
+        rm -f -- "${isofs_dir}/${install_dir}/grubenv"
         printf '%.1024s' "$(printf '# GRUB Environment Block\nNAME=%s\nVERSION=%s\n%s' \
             "${iso_name}" "${iso_version}" "$(printf '%0.1s' "#"{1..1024})")" \
             > "${isofs_dir}/${install_dir}/grubenv"