Justfile: add rebuild and update tasks for offline disk installations

Justfile

@@ -144,6 +144,43 @@ update-this-device rebuild-mode='switch':
 
 	git commit -v ${outfile} -m "nix/os/devices/$(hostname -s): bump versions"
 
+# Rebuild an offline system
+rebuild-disk device:
+	#!/usr/bin/env bash
+	set -xe
+
+	just -v disk-mount {{device}}
+	just -v disk-install {{device}}
+	just -v disk-umount {{device}}
+
+# Re-render the versions of the given offline system and reinstall it in offline-mode
+update-disk dir:
+	#!/usr/bin/env bash
+	set -exuo pipefail
+
+	dir={{dir}}
+
+	template={{dir}}/versions.tmpl.nix
+	outfile={{dir}}/versions.nix
+
+	if ! test -e ${template}; then
+		template="$(just _DEFAULT_VERSION_TMPL)"
+	fi
+
+	esh -o ${outfile} ${template}
+	if ! test "$(git diff ${outfile})"; then
+		echo Already on latest versions
+		exit 0
+	fi
+
+	export SYSREBUILD_LOG=.{{dir}}_sysrebuild.log
+	just -v rebuild-disk {{dir}} || {
+		echo ERROR: Update of {{dir}} failed, reverting ${outfile}...
+		exit 1
+	}
+
+	git commit -v ${outfile} -m "${dir}: bump versions"
+
 # Iterate on a qtile config by running it inside Xephyr. (un-/grab the mouse with Ctrl + Shift-L)
 hm-iterate-qtile:
 	#!/usr/bin/env bash