cmd-build-with-buildah: unify more the direct and non-direct paths

We now have persistent containers storage in the supermin VM
with the cache. Let's unify the direct and non-direct paths
in the code.

This does mean we need to skopeo copy to the ociarchive inside
the supermin VM (because we don't have access to that containers
storage outside of it). Alternatively we could have tried to
run the `cosa import` inside the supermin VM as well, but the
use of a bare-user repository over a virtiofs share made that
option not work.

Author: dustymabe

src/cmd-build-with-buildah

@@ -101,8 +101,6 @@ build_with_buildah() {
     # This is analogous to the chmod we do in cmdlib.sh in the legacy path.
     chmod -R gu-s "${tempdir}/src"
 
-    tmp_oci_archive_path=$(realpath "${tempdir}/out.ociarchive")
-
     initconfig="src/config.json"
     if [ -f "${initconfig}" ]; then
         variant="$(jq --raw-output '."coreos-assembler.config-variant"' "${initconfig}")"
@@ -169,31 +167,34 @@ build_with_buildah() {
         set -- "$@" -v "$(realpath overrides)":/run/src/overrides
     fi
 
-    if [ -n "$DIRECT" ]; then
-        # output to a tag since it's more convenient for development;
-        # buildah doesn't support doing both at once
-        # shellcheck disable=SC1090
-        osname=$(source "src/config/${argsfile}"; echo "${NAME}")
-        final_ref="containers-storage:localhost/${osname}:${VERSION}"
-    else
-        # In the supermin path ensure the ociarchive gets compressed
-        set -- "$@" --disable-compression=false
-        final_ref="oci-archive:${tmp_oci_archive_path}"
-    fi
+    # We'll also copy to an intermediate ociarchive file before
+    # passing that ociarchive to cosa import
+    tmp_oci_archive="oci-archive:$(realpath "${tempdir}/out.ociarchive")"
 
-    # and finally, add the tag and context dir
-    set -- "$@" -t "${final_ref}" .
+    # Set the output tag to be something unique
+    # shellcheck disable=SC1090
+    osname=$(source "src/config/${argsfile}"; echo "${NAME}")
+    final_ref="containers-storage:localhost/${osname}:${VERSION}"
+    # and add the unique tag and context dir to the command
+    set -- "$@" --tag "${final_ref}" .
 
     echo "Running:" buildah "$@"
     if [ -n "$DIRECT" ]; then
-        env -C "${tempdir}/src" buildah "$@"
+        cmd="bash"
     else
-        /usr/lib/coreos-assembler/cmd-supermin-run --cache \
-            env -C "${tempdir}/src" TMPDIR="$(realpath cache)" buildah "$@"
+        cmd="/usr/lib/coreos-assembler/cmd-supermin-run --cache"
     fi
+    cat <<EOF > "${tempdir}/build-with-buildah-script.sh"
+        set -euxo pipefail
+        env -C ${tempdir}/src TMPDIR=$(realpath cache) buildah $@
+        skopeo copy --quiet "${final_ref}" "${tmp_oci_archive}"
+EOF
+    chmod +x "${tempdir}/build-with-buildah-script.sh"
+    $cmd "${tempdir}/build-with-buildah-script.sh"
 
-    /usr/lib/coreos-assembler/cmd-import "${final_ref}" ${SKIP_PRUNE:+--skip-prune}
-
+    # Finally import the ociarchive
+    /usr/lib/coreos-assembler/cmd-import \
+        "${tmp_oci_archive}" ${SKIP_PRUNE:+--skip-prune}
     rm -rf "${tempdir}"
 }