revlog: map rev(wdirid) to WdirUnsupported exception

This will allow us to map repo["ff..."] to workingctx. _partialmatch() will
be updated later. I tried "return wdirrev" in place of raising the exception,
but earlier exception seemed better.

mercurial/revlog.py

@@ -26,6 +26,7 b' from .node import ('
     hex,
     nullid,
     nullrev,
+    wdirid,
     wdirrev,
 )
 from .i18n import _
@@ -416,6 +417,8 b' class revlog(object):'
             raise
         except RevlogError:
             # parsers.c radix tree lookup failed
+            if node == wdirid:
+                raise error.WdirUnsupported
             raise LookupError(node, self.indexfile, _('no node'))
         except KeyError:
             # pure python cache lookup failed
@@ -430,6 +433,8 b' class revlog(object):'
                 if v == node:
                     self._nodepos = r - 1
                     return r
+            if node == wdirid:
+                raise error.WdirUnsupported
             raise LookupError(node, self.indexfile, _('no node'))
 
     # Accessors for index entries.

mercurial/scmutil.py

@@ -190,6 +190,8 b' def callcatch(ui, func):'
         if inst.hint:
             ui.warn(_("(%s)\n") % inst.hint)
         return 1
+    except error.WdirUnsupported:
+        ui.warn(_("abort: working directory revision cannot be specified\n"))
     except error.Abort as inst:
         ui.warn(_("abort: %s\n") % inst)
         if inst.hint:

tests/test-debugcommands.t

@@ -110,6 +110,12 b' Test max chain len'
       7     6    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        2 (glob)
       8     7    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        3 (glob)
 
+Test WdirUnsupported exception
+
+  $ hg debugdata -c ffffffffffffffffffffffffffffffffffffffff
+  abort: working directory revision cannot be specified
+  [255]
+
 Test cache warming command
 
   $ rm -rf .hg/cache/