scmutil: 0-pad transaction report callback category

Before this patch, the transaction name was '%2i-txnreport', which
means the first one would be ' 0-txnreport'. It seems more intuitive
for sorting purposes (the callbacks are called in lexicographical
order) to make it 0-padded.

Differential Revision: https://phab.mercurial-scm.org/D1917

mercurial/scmutil.py

@@ -1247,7 +1247,7 b' def registersummarycallback(repo, otr, t'
             if filtername:
                 repo = repo.filtered(filtername)
             func(repo, tr)
-        newcat = '%2i-txnreport' % len(categories)
+        newcat = '%02i-txnreport' % len(categories)
         otr.addpostclose(newcat, wrapped)
         categories.append(newcat)
         return wrapped