resolve: don't abort resolve -l even when no merge is in progress

This broke some internal automation that was quite reasonably checking for
unresolved files as a way to determine whether a merge happened cleanly. We
still abort for resolve --mark etc.

mercurial/commands.py

@@ -4922,7 +4922,7 b' def resolve(ui, repo, *pats, **opts):'
 
     ms = mergemod.mergestate(repo)
 
-    if not ms.active():
+    if not ms.active() and not show:
         raise util.Abort(_('resolve command not applicable when not merging'))
 
     m = scmutil.match(repo[None], pats, opts)

tests/test-histedit-non-commute-abort.t

@@ -85,8 +85,6 b' abort the edit'
 
 log after abort
   $ hg resolve -l
-  abort: resolve command not applicable when not merging
-  [255]
   $ hg log --graph
   @  changeset:   6:bfa474341cc9
   |  tag:         tip

tests/test-resolve.t

@@ -42,9 +42,12 b' resolve the failure'
   no more unresolved files
   $ hg commit -m 'resolved'
 
-resolve -l should error since no merge in progress
+resolve -l should be empty
 
   $ hg resolve -l
+
+resolve -m should abort since no merge in progress
+  $ hg resolve -m
   abort: resolve command not applicable when not merging
   [255]
 

tests/test-shelve.t

@@ -262,8 +262,6 b' abort the unshelve and be happy'
   summary:     second
   
   $ hg resolve -l
-  abort: resolve command not applicable when not merging
-  [255]
   $ hg status
   A foo/foo
   ? a/a.orig