revsetbenchmark: get revision to benchmark in a function

And move it to proper subprocess call.

contrib/revsetbenchmarks.py

@@ -1,78 +1,85 b''
 #!/usr/bin/env python
 
 # Measure the performance of a list of revsets against multiple revisions
 # defined by parameter. Checkout one by one and run perfrevset with every
 # revset in the list to benchmark its performance.
 #
 # - First argument is a revset of mercurial own repo to runs against.
 # - Second argument is the file from which the revset array will be taken
 #   If second argument is omitted read it from standard input
 #
 # You should run this from the root of your mercurial repository.
 #
 # This script also does one run of the current version of mercurial installed
 # to compare performance.
 
 import sys
 from subprocess import check_call, check_output, CalledProcessError
 
 
 def update(rev):
     """update the repo to a revision"""
     try:
         check_call(['hg', 'update', '--quiet', '--check', str(rev)])
     except CalledProcessError, exc:
         print >> sys.stderr, 'update to revision %s failed, aborting' % rev
         sys.exit(exc.returncode)
 
 def perf(revset):
     """run benchmark for this very revset"""
     try:
         check_call(['./hg', '--config', 'extensions.perf=contrib/perf.py',
                     'perfrevset', revset])
     except CalledProcessError, exc:
         print >> sys.stderr, 'abort: cannot run revset benchmark'
         sys.exit(exc.returncode)
 
 def printrevision(rev):
     """print data about a revision"""
     sys.stdout.write("Revision: ")
     sys.stdout.flush()
     check_call(['hg', 'log', '--rev', str(rev), '--template',
                '{desc|firstline}\n'])
 
+def getrevs(spec):
+    """get the list of rev matched by a revset"""
+    try:
+        out = check_output(['hg', 'log', '--template={rev}\n', '--rev', spec])
+    except CalledProcessError, exc:
+        print >> sys.stderr, "abort, can't get revision from %s" % spec
+        sys.exit(exc.returncode)
+    return [r for r in out.split() if r]
+
+
 
 target_rev = sys.argv[1]
 
 revsetsfile = sys.stdin
 if len(sys.argv) > 2:
     revsetsfile = open(sys.argv[2])
 
 revsets = [l.strip() for l in revsetsfile]
 
 print "Revsets to benchmark"
 print "----------------------------"
 
 for idx, rset in enumerate(revsets):
     print "%i) %s" % (idx, rset)
 
 print "----------------------------"
 print
 
-revs = check_output("hg log --template='{rev}\n' --rev " + target_rev,
-                    shell=True)
 
-revs = [r for r in revs.split() if r]
+revs = getrevs(target_rev)
 
-# Benchmark revisions
 for r in revs:
     print "----------------------------"
     printrevision(r)
     print "----------------------------"
     update(r)
     for idx, rset in enumerate(revsets):
         sys.stdout.write("%i) " % idx)
         sys.stdout.flush()
         perf(rset)
     print "----------------------------"