Add --set to config append, --report to config {set,append,remove}

[manics]

What this PR does

Adds --set option to omero config append, to indicate a value should only be added if it's not already in the list, taking into account the defaults, see #4597

Adds --report option to omero config {append,set,remove}. This will always print out Changed: ... if a change was made, and nothing if no change was made.

Testing this PR

1. Check omero config append/set/remove behaves as before.

2. Try something like

   omero config append --set omero.web.ui.top_links '["History", "history", {"title": "History"}]'
   

   this should have no effect (E.g. omero config get, or omero web restart and check the top-links) because this value is part of the standard defaults.

3. Try it without --set, you should see the old behaviour i.e. the duplicate value is appended

   omero config append omero.web.ui.top_links '["History", "history", {"title": "History"}]'
   

4. Add a different value, e.g.

   omero config append --set omero.web.ui.top_links '["BBC", "http://www.bbc.co.uk/"]'
   

5. Try omero config {append,set,remove} --report. If a change was made you should see a message such as Changed: Appended omero.web.ui.top_links:["BBC", "http://www.bbc.co.uk/"]

The idea behind this is to assist with Ansible deployments where you want to programmatically know whether or not a change was made.

Related reading

• Idempotent configuration commands & config management #4597
• Motivation: Deploy mapr on the IDR with Ansible
  • Web apps: IDR Mapr infrastructure#104

[joshmoore]

Generally looks very useful. Primary thoughts are:

• append --set isn't very intuitive (for me). append --once ?
• remove could use a reciprocal flag. --all ?

cc: @ximenesuk -- with @manics away, do we want to copy this to the mainline for further investigation?

[joshmoore]

Merging for the 0.0.7 tag. If we decide to rename the properties, then this will need a follow-up to metadata52 (though on the mainline we can do it straight-away)

[joshmoore]

Note: new mapr PR which makes use of this feature: ome/infrastructure#108

[atarkowska]

--rebased-to #4828