destutil: show message about other branch heads, even if on a closed head

Before this patch, bare "hg update" displays message below, if there
is at least one non-closed branch head other than current parent:

   1. 'XX other heads for branch "BRANCH"' message, if current parent is
      on a non-closed branch head

      This suggests user to invoke "hg heads" or so for merging them.

   2. no message, if current parent is on a closed branch head

      At this patch, bare "hg update" might choose closed branch head
      as update destination, and it causes this situation easily.

   3. no message, otherwise (= current parent isn't on any branch head)

'XX other heads for branch "BRANCH"' should be displayed also in #2
case above, because user might overlook other non-closed branch heads.

This patch gets a list of all branch heads regardless of closed-ness
of it, and uses it (= 'allheads') to distinguish #1/#2 from #3 above.

mercurial/destutil.py

@@ -358,9 +358,10 @@ def _statusotherbook(ui, repo):
 
 def _statusotherbranchheads(ui, repo):
     currentbranch = repo.dirstate.branch()
+    allheads = repo.branchheads(currentbranch, closed=True)
     heads = repo.branchheads(currentbranch)
-    if repo.revs('%ln and parents()', heads):
-        # we are on a head
+    if repo.revs('%ln and parents()', allheads):
+        # we are on a head, even though it might be closed
         otherheads = repo.revs('%ln - parents()', heads)
         if otherheads:
             ui.status(_('%i other heads for branch "%s"\n') %

tests/test-update-branches.t

@@ -175,6 +175,41 @@ Cases are run as shown in that table, row by row.
   parent=1
   M foo
 
+  $ cd ..
+
+Test updating with closed head
+---------------------------------------------------------------------
+
+  $ hg clone -U -q b1 closed-heads
+  $ cd closed-heads
+
+Test updating if at least one non-closed branch head exists
+
+if on the closed branch head:
+- updating is no-op
+- "N other heads for ...." message is displayed
+
+  $ hg update -q -C 3
+  $ hg commit --close-branch -m 6
+  $ norevtest "on closed branch head" clean 6
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  1 other heads for branch "default"
+  parent=6
+
+Test updating if all branch heads are closed
+
+if on the closed branch head:
+- updating is no-op
+- "N other heads for ...." message isn't displayed
+
+  $ hg update -q -C 2
+  $ hg commit --close-branch -m 7
+  $ norevtest "all heads of branch default are closed" clean 6
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  parent=6
+
+  $ cd ../b1
+
 Test obsolescence behavior
 ---------------------------------------------------------------------