Clean up GCE image build

In line with the others, support any file names on input.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

base/mkimage-gce/Dockerfile

@@ -1,10 +1,6 @@
 # Tag: 8719f0f33b3cf9d59a62be64a42220978ac96486
 FROM mobylinux/guestfs@sha256:c7229f01c1a54270d2bc3597c30121628c18db211ed32fb7202823b6eaa4f853
 
-WORKDIR /tmp/image
-
 COPY . .
 
-COPY make-gce /usr/bin
-
-CMD [ "/usr/bin/make-gce" ]
+CMD [ "/make-gce" ]

base/mkimage-gce/Makefile

@@ -4,7 +4,7 @@ IMAGE=mkimage-gce
 
 default: push
 
-hash: Dockerfile make-gce syslinux.cfg
+hash: Dockerfile make-gce
 	tar cf - $^ | docker build --no-cache -t $(IMAGE):build -
 	docker run --rm $(IMAGE):build sh -c "(cat $^; apt list --installed 2>/dev/null) | sha1sum" | sed 's/ .*//' > hash
 

base/mkimage-gce/make-gce

@@ -2,13 +2,42 @@
 
 set -e
 
+mkdir -p /tmp/image
+cd /tmp/image
+
 # input is a tarball of vmlinuz64 and initrd.img on stdin
 # output is a compressed tarball of a raw disk image on stdout
 
 mkdir -p files
-tar xf - -C files
 
-cp syslinux.cfg files
+cd files
+
+# extract. As guestfs base is currently Debian, no compression support
+# only if stdin is a tty, if so need files volume mounted...
+[ -t 0 ] || tar xf -
+
+INITRD="$(find . -name '*.img')"
+KERNEL="$(find . -name vmlinuz64 -or -name bzImage)"
+
+[ "$KERNEL" = "./vmlinuz64" ] || mv "$KERNEL" vmlinuz64
+[ "$INITRD" = "./initrd.img" ] || mv "$INITRD" initrd.img
+
+# clean up subdirectories
+find . -mindepth 1 -maxdepth 1 -type d | xargs rm -rf
+
+# should be externally provided as GCE specific
+GCE_CONFIG="earlyprintk=ttyS0,115200 console=ttyS0,115200 mobyplatform=gcp vsyscall=emulate"
+
+CFG="DEFAULT linux
+LABEL linux
+    KERNEL /vmlinuz64
+    INITRD /initrd.img
+    APPEND $GCE_CONFIG $*
+"
+
+printf "$CFG" > syslinux.cfg
+
+cd ..
 
 tar cf files.tar -C files .
 

base/mkimage-gce/syslinux.cfg

@@ -1,5 +0,0 @@
-DEFAULT linux
-LABEL linux
-    KERNEL /vmlinuz64
-    INITRD /initrd.img
-    APPEND earlyprintk=ttyS0,115200 console=ttyS0,115200 mobyplatform=gcp vsyscall=emulate