uncommit: don't allow bare uncommit on dirty working directory

As per IRC discussion and suggestion by Augie, we should not allow bare `hg
uncommit` on dirty working directory.

Differential Revision: https://phab.mercurial-scm.org/D734

hgext/uncommit.py

@@ -22,6 +22,7 b' from __future__ import absolute_import'
 from mercurial.i18n import _
 
 from mercurial import (
+    cmdutil,
     commands,
     context,
     copies,
@@ -148,6 +149,8 b' def uncommit(ui, repo, *pats, **opts):'
     with repo.wlock(), repo.lock():
         wctx = repo[None]
 
+        if not pats:
+            cmdutil.bailifchanged(repo)
         if wctx.parents()[0].node() == node.nullid:
             raise error.Abort(_("cannot uncommit null changeset"))
         if len(wctx.parents()) > 1:

tests/test-uncommit.t

@@ -149,6 +149,9 b' Uncommit with dirty state'
   foo
   $ hg status
   M files
+  $ hg uncommit
+  abort: uncommitted changes
+  [255]
   $ hg uncommit files
   $ cat files
   abcde
@@ -337,7 +340,7 b' Add and expect uncommit to fail on both '
   (branch merge, don't forget to commit)
 
   $ hg uncommit
-  abort: cannot uncommit while merging
+  abort: outstanding uncommitted merge
   [255]
 
   $ hg status