perfbranchmap: allow to select the filter to benchmark

Running the branchmap computation on all filter levels can be expensive.
Narrowing the run to some specific filters can speed up benchmarking time when
working only on a subset of filter levels.

contrib/perf.py

@@ -1568,11 +1568,13 b' def perfvolatilesets(ui, repo, *names, *'
           ('', 'clear-revbranch', False,
            'purge the revbranch cache between computation'),
          ] + formatteropts)
-def perfbranchmap(ui, repo, full=False, clear_revbranch=False, **opts):
+def perfbranchmap(ui, repo, *filternames, **opts):
     """benchmark the update of a branchmap
 
     This benchmarks the full repo.branchmap() call with read and write disabled
     """
+    full = opts.get("full", False)
+    clear_revbranch = opts.get("clear_revbranch", False)
     timer, fm = gettimer(ui, opts)
     def getbranchmap(filtername):
         """generate a benchmark function for the filtername"""
@@ -1591,6 +1593,8 b' def perfbranchmap(ui, repo, full=False, '
         return d
     # add filter in smaller subset to bigger subset
     possiblefilters = set(repoview.filtertable)
+    if filternames:
+        possiblefilters &= set(filternames)
     subsettable = getbranchmapsubsettable()
     allfilters = []
     while possiblefilters:
@@ -1607,8 +1611,9 b' def perfbranchmap(ui, repo, full=False, '
     if not full:
         for name in allfilters:
             repo.filtered(name).branchmap()
-    # add unfiltered
-    allfilters.append(None)
+    if not filternames or 'unfiltered' in filternames:
+        # add unfiltered
+        allfilters.append(None)
 
     branchcacheread = safeattrsetter(branchmap, 'read')
     branchcachewrite = safeattrsetter(branchmap.branchcache, 'write')