Addition of add-sparse-env-var-to-agent-sv.bash

Contributes to orange-cloudfoundry/paas-templates#2060

Still need testing

[skip ci]

jobs/k3s-agent/templates/bin/add-sparse-env-var-to-agent-sv.bash

@@ -0,0 +1,19 @@
+#!/bin/bash
+
+set -x
+set -e
+
+#TODO: test whether the bosh job indeed runs as vcap, if running as root, we can remove next line
+[ $(id -u) -eq 0 ] || exec sudo $0 $@
+
+if ! grep TAR_OPTIONS /etc/sv/agent/run ; then
+  echo "patching /etc/sv/agent/run to inject TAR_OPTIONS as a workaround for https://github.com/orange-cloudfoundry/paas-templates/issues/2060"
+  # substitute 3rd line with new export
+  # more about this syntax at https://stackoverflow.com/a/9533736/1484823
+  sed -i.orig '3s/$^export TAR_OPTIONS=" --sparse "/'
+  #FIXME: check that the creation of a backup file /etc/sv/agent/run.orig is ignored by sv
+  # if not, replace -i.orig flag by -i flag
+else
+  echo "/etc/sv/agent/run already contains TAR_OPTIONS"
+fi
+! diff /etc/sv/agent/run /etc/sv/agent/run.orig