graft: abort if --date/user specified with --currentdate/currentuser (BC)

They are conflicting options. Let's explicitly ban such combination.

Note that this means you need "--no-currentdate --date" to override
--currentdate specified in aliases/defaults.

mercurial/commands.py

@@ -2393,6 +2393,10 b' def _dograft(ui, repo, *revs, **opts):'
     # list of new nodes created by ongoing graft
     statedata['newnodes'] = []
 
+    if opts.get('user') and opts.get('currentuser'):
+        raise error.Abort(_('--user and --currentuser are mutually exclusive'))
+    if opts.get('date') and opts.get('currentdate'):
+        raise error.Abort(_('--date and --currentdate are mutually exclusive'))
     if not opts.get('user') and opts.get('currentuser'):
         opts['user'] = ui.username()
     if not opts.get('date') and opts.get('currentdate'):

tests/test-graft.t

@@ -112,6 +112,16 b' Specify revisions with -r:'
   skipping ancestor revision 1:5d205f8b35b6
   [255]
 
+Conflicting date/user options:
+
+  $ hg up -q 0
+  $ hg graft -U --user foo 2
+  abort: --user and --currentuser are mutually exclusive
+  [255]
+  $ hg graft -D --date '0 0' 2
+  abort: --date and --currentdate are mutually exclusive
+  [255]
+
 Can't graft with dirty wd:
 
   $ hg up -q 0