spec: clean old fedup junk and migrate pkg cache

If we're replacing fedup, then we should clean up old fedup junk - boot
images, bootloader entry, /system-upgrade symlink, etc. - but we should
try to keep the package cache, if possible, so the user doesn't have to
download everything again.

The easiest way to handle this is to do it in %pre, so we can move the
cache and then just tell fedup to clean up whatever's left *before* it
gets deleted.

Resolves: rhbz#1264948

dnf-plugin-system-upgrade.spec

@@ -77,6 +77,18 @@ make install-plugin DESTDIR=$RPM_BUILD_ROOT PYTHON=%{__python3}
 make check PYTHON=%{__python2}
 make check PYTHON=%{__python3}
 
+%pre
+# if we're replacing fedup, we need to make sure it cleans up its leftovers.
+# (see https://bugzilla.redhat.com/show_bug.cgi?id=1264948)
+if [ "$1" == 1 -a -x /usr/bin/fedup ]; then
+    # save the old package cache (if the new one isn't populated)
+    if [ -d /var/lib/system-upgrade ]; then
+        mv -f -T /var/lib/system-upgrade /var/lib/dnf/system-upgrade || :
+    fi
+    # clean up everything else
+    /usr/bin/fedup --clean || :
+fi
+
 %files -f %{name}.lang
 %license LICENSE
 %doc README.md