main/postmarketos-base: force migration of installs to /usr merge

This carries some risks, but we are willing to put up with them. We
need everybody to have a /usr-merge to continue moving on our
priorities. Fortunately, the merge-usr script has received quite a lot
of testing so far.

main/postmarketos-base/APKBUILD

@@ -1,6 +1,6 @@
 pkgname=postmarketos-base
 pkgver=45
-pkgrel=0
+pkgrel=1
 pkgdesc="Meta package for minimal postmarketOS base"
 url="https://postmarketos.org"
 arch="noarch"
@@ -15,6 +15,7 @@ depends="
 	busybox-suid
 	devicepkg-utils>=0.2.0
 	eudev
+	merge-usr
 	musl-utils
 	openssh-server-pam
 	postmarketos-keys
@@ -27,7 +28,7 @@ _pmb_recommends="
 	doas
 	doas-sudo-shim
 "
-install="$pkgname.post-install"
+install="$pkgname.post-install $pkgname.post-upgrade"
 triggers="$pkgname.trigger=/usr/share/deviceinfo"
 subpackages="
 	$pkgname-mesa

main/postmarketos-base/postmarketos-base.post-upgrade

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+if [ -d /bin -a ! -L /bin ] || \
+       [ -d /sbin -a ! -L /sbin ] || \
+       [ -d /lib -a ! -L /lib ]; then
+    echo "INFO: /usr merge dryrun to check for errors"
+    if merge-usr --dryrun ; then
+        echo "INFO: Doing the /usr merge"
+        merge-usr
+        exit $?
+    else
+        echo "Error trying the /usr merge!"
+        exit 1
+    fi
+fi