perf: fallback to subset if ondisk cache is missing in perfbranchmapload

If there is no branchmap on disk for that filter, it means that the cache from
some subset's filter is relevant for this one. We look for it instead of
aborting.

That way it is much simpler to run the command in an automated way. We can now
add it to `test-contrib-perf.t`.

contrib/perf.py

@@ -2247,17 +2247,24 def perfbranchmapload(ui, repo, filter=b
                 ui.status(b'%s - %s\n'
                           % (filtername, util.bytecount(st.st_size)))
         return
-    if filter:
+    if not filter:
+        filter = None
+    subsettable = getbranchmapsubsettable()
+    if filter is None:
+        repo = repo.unfiltered()
+    else:
         repo = repoview.repoview(repo, filter)
-    else:
-        repo = repo.unfiltered()
 
     repo.branchmap() # make sure we have a relevant, up to date branchmap
 
+    currentfilter = filter
     # try once without timer, the filter may not be cached
-    if branchmap.read(repo) is None:
+    while branchmap.read(repo) is None:
+        currentfilter = subsettable.get(currentfilter)
+        if currentfilter is None:
         raise error.Abort(b'No branchmap cached for %s repo'
                           % (filter or b'unfiltered'))
+        repo = repo.filtered(currentfilter)
     timer, fm = gettimer(ui, opts)
     def setup():
         if clearrevlogs:

tests/test-contrib-perf.t

@@ -143,6 +143,7 perfstatus
   $ hg perfunidiff --alldata 1
   $ hg perfbookmarks
   $ hg perfbranchmap
+  $ hg perfbranchmapload
   $ hg perfcca
   $ hg perfchangegroupchangelog
   $ hg perfchangegroupchangelog --cgversion 01