commit: allow to close branch when committing change over a closed head

Otherwise, an explicit other commit become necessary, which seems both silly and
verbose.

This is useful when merging closed heads on the same branches, for example when
merging multiple repositories together.

mercurial/commands.py

@@ -2087,10 +2087,17 b' def _docommit(ui, repo, *pats, **opts):'
         extra[b'close'] = b'1'
 
         if repo[b'.'].closesbranch():
-            raise error.InputError(
-                _(b'current revision is already a branch closing head')
-            )
-        elif not bheads:
+            # Not ideal, but let us do an extra status early to prevent early
+            # bail out.
+            matcher = scmutil.match(repo[None], pats, opts)
+            s = repo.status(match=matcher)
+            if s.modified or s.added or s.removed:
+                bheads = repo.branchheads(branch, closed=True)
+            else:
+                msg = _(b'current revision is already a branch closing head')
+                raise error.InputError(msg)
+
+        if not bheads:
             raise error.InputError(
                 _(b'branch "%s" has no heads to close') % branch
             )

tests/test-branches.t

@@ -283,6 +283,19 b' verify update will accept invalid legacy'
   abort: current revision is already a branch closing head
   [10]
 
+  $ echo foo > b
+  $ hg commit -d '9 0' --close-branch -m 're-closing this branch'
+
+  $ echo bar > b
+  $ hg commit -d '9 0' --close-branch -m 're-closing this branch' bh1
+  abort: current revision is already a branch closing head
+  [10]
+  $ hg commit -d '9 0' --close-branch -m 're-closing this branch' b
+
+  $ hg debugstrip --rev 13: --no-backup
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg revert --all --no-backup
+
   $ hg log -r tip --debug
   changeset:   12:e3d49c0575d8fc2cb1cd6859c747c14f5f6d499f
   branch:      b