ec ioc instances may fail

[gilesknap]

• it does not show any new iocs that have never changed
• it gets an error if one of the tags is on the 1st commit

  (venv) (dev) [hgv27681@pc0116 bl38p]$ ec ioc instances bl38p-ea-ioc-03
  Available instance versions for bl38p-ea-ioc-03:
  ERROR:  Command Failed:
  git diff --name-only 2023.10.1 2023.10.1^
  fatal: ambiguous argument '2023.10.1^': unknown revision or path not in the working tree.
  Use '--' to separate paths from revisions, like this:
  'git <command> [<revision>...] -- [<file>...]'

[gilesknap]

this is fixed