stack/cacuase: Make rerequest updatable

It will generate new csr and key if the template changes, also if beacuse of
some reason key or csr is not present anymore.

This change makes the part resist to cases when it is becoming uninstalled and
installed again, so that it will not shoot its own foot and leaving the macro
user in inconsistent state.

stack/caucase/buildout.hash.cfg

@@ -15,4 +15,4 @@
 
 [caucase-jinja2-library]
 filename = caucase.jinja2.library
-md5sum = 0c9b50ff49e0ca0e8e2bc70ec0fd9431
+md5sum = 5cf324ea1beb593738339f3d20d60a44

stack/caucase/caucase.jinja2.library

@@ -108,5 +108,15 @@ command-line = '{{ buildout_bin_directory }}/caucase-updater'
 {% macro rerequest(prefix, buildout_bin_directory, template, csr, key) -%}
 [{{ prefix }}]
 recipe = plone.recipe.command
-command = '{{ buildout_bin_directory }}/caucase-rerequest' --template '{{ template }}' --csr '{{ csr }}' --key '{{ key }}'
+checksum-file = '{{ template }}.md5'
+command =
+  set -e
+  md5_current=$(${buildout:executable} -c "import hashlib ; hashlib.md5(open('{{ template }}').read()).hexdigest()")
+  md5_old=$([ -f ${:checksum-file} ] && cat ${:checksum-file} || echo none)
+  if [ "$md5_current" != "$md5_old" ] || [ ! -f '{{ csr }}' ] || [ ! -f '{{ key }}' ] ; then
+    '{{ buildout_bin_directory }}/caucase-rerequest' --template '{{ template }}' --csr '{{ csr }}' --key '{{ key }}'
+    echo $md5_current > ${:checksum-file}
+  fi
+update-command = ${:command}
+stop-on-error = True
 {%- endmacro %}