unshelve: add abort on using continue and interactive together

`unshelve --continue --interactive` will not work as expected by the
user as the mode of in-progress unshelve is preserved and cannot be
overwritten. This patch makes `unshelve` to throw an error on using
both `--continue` and `--interactive` together with `unshelve`.

Differential Revision: https://phab.mercurial-scm.org/D6703

mercurial/shelve.py

@@ -954,6 +954,8 b' def dounshelve(ui, repo, *shelved, **opt'
         state = _loadshelvedstate(ui, repo, opts)
         if abortf:
             return unshelveabort(ui, repo, state)
+        elif continuef and interactive:
+            raise error.Abort(_('cannot use both continue and interactive'))
         elif continuef:
             return unshelvecontinue(ui, repo, state, opts)
     elif len(shelved) > 1:

tests/test-shelve.t

@@ -1347,6 +1347,12 b' Abort unshelve while merging (issue5123)'
   $ hg resolve -m bar1 bar2
   (no more unresolved files)
   continue: hg unshelve --continue
+
+-- using --continue with --interactive should throw an error
+  $ hg unshelve --continue -i
+  abort: cannot use both continue and interactive
+  [255]
+
   $ cat bar1
   A
   B