ui: give editor() a tag of its own

We know that calls to ui.editor() always block on the user's configured editor.
Use a blocking tag that ensures that we don't see a huge variety of editor
options in our logging.

mercurial/ui.py

@@ -1139,7 +1139,8 b' class ui(object):'
 
             self.system("%s \"%s\"" % (editor, name),
                         environ=environ,
-                        onerr=error.Abort, errprefix=_("edit failed"))
+                        onerr=error.Abort, errprefix=_("edit failed"),
+                        blockedtag='editor')
 
             f = open(name)
             t = f.read()