snap: Use SNAP_USER_COMMON as HOME

This prevents the config and the user collection from being
backed up by snapd on update. If the user reverts qelectrotech,
the current collection will thus not be overwritten by the
possibly outdated backup.

Add a migration script that automatically transfers the user's .qet
directory to the new location.

build-aux/snap/local/launchers/qelectrotech-launch

@@ -1,5 +1,15 @@
-#!/bin/bash
+#!/bin/sh
 
+# migrate .qet directory from SNAP_USER_DATA to SNAP_USER_COMMON
+from="$SNAP_USER_DATA/.qet"
+to="$SNAP_USER_COMMON/.qet"
+if [ ! -d "$to" ] && [ -d "$from" ]; then
+  echo "Migrating user data from $from to $to"
+  mkdir "$to"
+  cp -av "$from/." "$to"
+fi
+
+# link DXFtoQET so that QET finds it
 mkdir -p "$HOME/.qet"
 ln -snf "$SNAP/bin/DXFtoQET" "$HOME/.qet/DXFtoQET"
 

build-aux/snap/snapcraft.yaml

@@ -28,8 +28,9 @@ apps:
     environment: &env
       __EGL_VENDOR_LIBRARY_DIRS: $SNAP/kf5/usr/share/glvnd/egl_vendor.d:$SNAP/usr/share/glvnd/egl_vendor.d
       TCL_LIBRARY: $SNAP/usr/share/tcltk/tcl8.6
-        QT_QPA_PLATFORMTHEME: gtk3
-        QT_AUTO_SCREEN_SCALE_FACTOR: 1
+      QT_QPA_PLATFORMTHEME: gtk3
+      QT_AUTO_SCREEN_SCALE_FACTOR: 1
+      HOME: $SNAP_USER_COMMON
 
   qet-tb-generator:
     command: bin/qelectrotech-launch $SNAP/bin/qet_tb_generator