revsetlang: perform quoting using ui.escapestr instead of repr()

This changes one of the doctest results, but I'm pretty sure on
inspection that it's an equivalent result.

mercurial/revsetlang.py

@@ -15,6 +15,7 b' from . import ('
     node,
     parser,
     pycompat,
+    util,
 )
 
 elements = {
@@ -581,11 +582,11 b' def _quote(s):'
     >>> _quote("asdf'\"")
     '\'asdf\\\'"\''
     >>> _quote('asdf\'')
-    '"asdf\'"'
+    "'asdf\\''"
     >>> _quote(1)
     "'1'"
     """
-    return repr(str(s))
+    return "'%s'" % util.escapestr('%s' % s)
 
 def formatspec(expr, *args):
     '''