[stellation-res] Eclipse Client: Action Enablement Code Checkin

[Jim Wright - IBM Research <jwright@xxxxxxxxxxxxxx>]

I've just checked in a set of changes to both
stellation.scm.model and stellation.scm.ui.

These changes provide initial support for action enablement,
for both toolbar and popup menu items, as follows:

* Checkin is enabled only when the local image is modified since checkout
  (This means you can select and check in multiple projects simultaneously).

* Fork is enabled only when exactly one Stellation project is associated
  with the current selection (You can't Fork > 1 project simultaneously)

* Checkout is enabled if there is either > 1 version in the current branch,
  or > 1 branches in the current project.

* Merge is enabled only when there are > 1 branches in the current project.

* Info is always enabled.

I'm not sure all of these enablement criteria are correct:
? Should Checkin be allowed for multiple projects? (It is now)
? Should Checkout be allowed for multiple projects? (It is now,
   but I think that's wrong)

Comments welcome!

I just realized that Merge is enabled with multiple projects in the 
selection --
that's clearly wrong, and I'll fix it soon.

Toolbar enablement currently has a glitch: most items are initially disabled.
To update enablement, you must change the selection in the Package Explorer
or Resource Navigator.  There's a timing problem (between the time when the
current selection is initially broadcast, and the time that the toolbar items
are initially updated) and I'm not quite sure how to solve it yet.

Regards -

  - Jim
--
Jim Wright, IBM T.J. Watson Research Center
*** The Stellation project: Advanced SCM for Collaboration
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