debugbuilddag: use '%d' instead of str() to get numbered lines

Differential Revision: https://phab.mercurial-scm.org/D2346

mercurial/debugcommands.py

@@ -163,7 +163,7 b' def debugbuilddag(ui, repo, text=None,'
     if mergeable_file:
         linesperrev = 2
         # make a file with k lines per rev
-        initialmergedlines = [str(i) for i in xrange(0, total * linesperrev)]
+        initialmergedlines = ['%d' % i for i in xrange(0, total * linesperrev)]
         initialmergedlines.append("")
 
     tags = []