revsetbenchmarks: use a more compact output format with a header

We change the output from:

  revset  #0: draft()
  0) wall 0.011989 comb 0.010000 user 0.000000 sys 0.010000 (best of 177)
  1) wall 0.012226 comb 0.010000 user 0.000000 sys 0.010000 (best of 193)
  2) wall 0.011838 comb 0.020000 user 0.000000 sys 0.020000 (best of 208)

to:

  revset  #0: draft()
       wall       comb       user       sys       count
  0)   0.012028   0.010000   0.000000   0.010000    170
  1)   0.012218   0.010000   0.000000   0.010000    157
  2)   0.012622   0.010000   0.000000   0.010000    189

This opens the road to more useful output.

contrib/revsetbenchmarks.py

@@ -111,12 +111,23 b' def idxwidth(nbidx):'
 def printresult(idx, data, maxidx):
     """print a line of result to stdout"""
     mask = '%%0%ii) %%s' % idxwidth(maxidx)
+    out = ['%10.6f' % data['wall'],
+           '%10.6f' % data['comb'],
+           '%10.6f' % data['user'],
+           '%10.6f' % data['sys'],
+           '%6d'    % data['count'],
+          ]
+    print mask % (idx, ' '.join(out))
 
-    out = ("wall %f comb %f user %f sys %f (best of %d)"
-           % (data['wall'], data['comb'], data['user'],
-              data['sys'], data['count']))
-
-    print mask % (idx, out)
+def printheader(maxidx):
+    header = [' ' * (idxwidth(maxidx) + 1),
+              '  %-8s' % 'wall',
+              '  %-8s' % 'comb',
+              '  %-8s' % 'user',
+              '  %-8s' % 'sys',
+              '%6s' % 'count',
+             ]
+    print ' '.join(header)
 
 def getrevs(spec):
     """get the list of rev matched by a revset"""
@@ -172,6 +183,7 b' for r in revs:'
     update(r)
     res = []
     results.append(res)
+    printheader(len(revsets))
     for idx, rset in enumerate(revsets):
         data = perf(rset, target=options.repo)
         res.append(data)
@@ -198,6 +210,7 b' print'
 for ridx, rset in enumerate(revsets):
 
     print "revset #%i: %s" % (ridx, rset)
+    printheader(len(results))
     for idx, data in enumerate(results):
         printresult(idx, data[ridx], len(results))
     print