discovery: move handling of sampling special case inside sampling function

The handling of cases where the number of revisions to sample is smaller than
the sample size can be moved with the sample function themselves. This
simplifies main logic, preparing a coming refactoring.

mercurial/setdiscovery.py

@@ -102,6 +102,8 b' def _takequicksample(repo, headrevs, rev'
     :headrevs: set of head revisions in local DAG to consider
     :revs: set of revs to discover
     :size: the maximum size of the sample"""
+    if len(revs) <= size:
+        return list(revs)
     sample = set(repo.revs('heads(%ld)', revs))
 
     if len(sample) >= size:
@@ -112,6 +114,8 b' def _takequicksample(repo, headrevs, rev'
     return sample
 
 def _takefullsample(repo, headrevs, revs, size):
+    if len(revs) <= size:
+        return list(revs)
     sample = set(repo.revs('heads(%ld)', revs))
 
     # update from heads
@@ -264,10 +268,7 b' def findcommonheads(ui, local, remote,'
             ui.debug("taking quick initial sample\n")
             samplefunc = _takequicksample
             targetsize = initialsamplesize
-        if len(undecided) <= targetsize:
-            sample = list(undecided)
-        else:
-            sample = samplefunc(local, ownheads, undecided, targetsize)
+        sample = samplefunc(local, ownheads, undecided, targetsize)
 
         roundtrips += 1
         progress.update(roundtrips)