log: fix limit vs order issue

sql is such a fuss...

test/test_tsio.py

@@ -369,6 +369,9 @@ def test_changeset_metadata(engine, tsh):
     meta = tsh.changeset_metadata(engine, log[0]['rev'])
     assert meta == {'foo': 'A', 'bar': 42}
 
+    log = tsh.log(engine, names=['ts-cs-metadata'], limit=1)
+    assert len(log) == 1
+
 
 def test_revision_date(engine, tsh):
     for i in range(1, 5):

tshistory/tsio.py

@@ -503,9 +503,9 @@ class timeseries(SeriesServices):
         if todate:
             q.where('cset.insertion_date <= %(todate)s', todate=todate)
 
+        q.option('order by cset.id desc')
         if limit:
             q.option('limit %(limit)s', limit=limit)
-        q.option('order by cset.id desc')
 
         rset = q.do(cn)
         for csetid, author, revdate, meta in rset.fetchall():