py3: fix sorting of obsolete markers in obsutil (issue6217) stable

py3: fix sorting of obsolete markers in obsutil (issue6217)

This is similar to 01e8eefd9434 and others. We move the sortedmarkers()
function from exchange module to obsutil.

--- a/mercurial/exchange.py	Wed Nov 06 16:54:34 2019 +0100
+++ b/mercurial/exchange.py	Sat Nov 09 10:31:58 2019 +0100
@@ -28,6 +28,7 @@
     logexchange,
     narrowspec,
     obsolete,
+    obsutil,
     phases,
     pushkey,
     pycompat,
@@ -99,11 +100,6 @@
     contentopts = attr.ib()
 
 
-def _sortedmarkers(markers):
-    # last item of marker tuple ('parents') may be None or a tuple
-    return sorted(markers, key=lambda m: m[:-1] + (m[-1] or (),))
-
-
 def parsebundlespec(repo, spec, strict=True):
     """Parse a bundle string specification into parts.
 
@@ -1140,7 +1136,7 @@
         return
     pushop.stepsdone.add(b'obsmarkers')
     if pushop.outobsmarkers:
-        markers = _sortedmarkers(pushop.outobsmarkers)
+        markers = obsutil.sortedmarkers(pushop.outobsmarkers)
         bundle2.buildobsmarkerspart(bundler, markers)
 
 
@@ -1475,7 +1471,7 @@
     if pushop.outobsmarkers:
         pushop.ui.debug(b'try to push obsolete markers to remote\n')
         rslts = []
-        markers = _sortedmarkers(pushop.outobsmarkers)
+        markers = obsutil.sortedmarkers(pushop.outobsmarkers)
         remotedata = obsolete._pushkeyescape(markers)
         for key in sorted(remotedata, reverse=True):
             # reverse sort to ensure we end with dump0
@@ -2573,7 +2569,7 @@
             heads = repo.heads()
         subset = [c.node() for c in repo.set(b'::%ln', heads)]
         markers = repo.obsstore.relevantmarkers(subset)
-        markers = _sortedmarkers(markers)
+        markers = obsutil.sortedmarkers(markers)
         bundle2.buildobsmarkerspart(bundler, markers)
 
 

--- a/mercurial/obsutil.py	Wed Nov 06 16:54:34 2019 +0100
+++ b/mercurial/obsutil.py	Sat Nov 09 10:31:58 2019 +0100
@@ -112,6 +112,11 @@
         yield marker(repo, markerdata)
 
 
+def sortedmarkers(markers):
+    # last item of marker tuple ('parents') may be None or a tuple
+    return sorted(markers, key=lambda m: m[:-1] + (m[-1] or (),))
+
+
 def closestpredecessors(repo, nodeid):
     """yield the list of next predecessors pointing on visible changectx nodes
 
@@ -675,7 +680,7 @@
             #   Having none means pruned node, multiple successors means split,
             #   single successors are standard replacement.
             #
-            for mark in sorted(succmarkers[current]):
+            for mark in sortedmarkers(succmarkers[current]):
                 for suc in mark[1]:
                     if suc not in cache:
                         if suc in stackedset:
@@ -712,7 +717,7 @@
                 # duplicated entry and successors set that are strict subset of
                 # another one.
                 succssets = []
-                for mark in sorted(succmarkers[current]):
+                for mark in sortedmarkers(succmarkers[current]):
                     # successors sets contributed by this marker
                     base = _succs()
                     base.markers.add(mark)