plymouth0.7: Launch plymouth --show-splash from udev event, and once before switch_root in case it didn't start

modules.d/50plymouth/52-plymouth-start.rules

@@ -0,0 +1 @@
+ACTION=="add", SUBSYSTEM=="graphics", KERNEL=="fb[0-9]*", RUN+="/bin/plymouth --show-splash"

modules.d/50plymouth/install

@@ -1,6 +1,6 @@
 #!/bin/bash
 . "$moddir"/plymouth-populate-initrd
-inst_hook pre-udev 10 "$moddir"/plymouth-start.sh
+inst_hook pre-udev 10 "$moddir"/plymouth-prep.sh
 inst_hook pre-pivot 90 "$moddir"/plymouth-newroot.sh
 inst_hook emergency 50 "$moddir"/plymouth-emergency.sh
 inst "$moddir"/cryptroot-ask.sh /sbin/cryptroot-ask
@@ -10,4 +10,4 @@ for modname in `find "/lib/modules/$kernel/kernel/drivers/gpu/drm" -name '*.ko'`
     instmods $modname
   fi
 done
-
+inst_rules "$moddir/52-plymouth-start.rules"

modules.d/50plymouth/plymouth-newroot.sh

@@ -1,4 +1,6 @@
 #!/bin/sh
 
-[ -x /bin/plymouth ] && /bin/plymouth --newroot=$NEWROOT
-
+if [ -x /bin/plymouth ]; then
+  /bin/plymouth --show-splash
+  /bin/plymouth --newroot=$NEWROOT
+fi

modules.d/50plymouth/plymouth-prep.sh

@@ -27,5 +27,4 @@ mknod /dev/ttyS3 c 4 67
 /lib/udev/console_init tty0
 
 [ -x /bin/plymouthd ] && /bin/plymouthd 
-[ -x /bin/plymouth ] && /bin/plymouth --show-splash