cleanupnodes: drop special casing around prune markers (API)

The `cleanupnodes` has logic to skip the creation of "prune" markers if the
changeset is already obsolete. This feels strange and gets in the way of code
changes to tracks folds. Now that callers no longer request such prune, we can
drop this logic.

In many cases, pruning through cleanupnodes should be replaced by internal
phase usage.

mercurial/scmutil.py

@@ -980,15 +980,13 b' def cleanupnodes(repo, replacements, ope'
             # Also sort the node in topology order, that might be useful for
             # some obsstore logic.
             # NOTE: the filtering and sorting might belong to createmarkers.
-            isobs = unfi.obsstore.successors.__contains__
             torev = unfi.changelog.rev
             sortfunc = lambda ns: torev(ns[0][0])
             rels = []
             for ns, s in sorted(replacements.items(), key=sortfunc):
                 for n in ns:
-                    if s or not isobs(n):
-                        rel = (unfi[n], tuple(unfi[m] for m in s))
-                        rels.append(rel)
+                    rel = (unfi[n], tuple(unfi[m] for m in s))
+                    rels.append(rel)
             if rels:
                 obsolete.createmarkers(repo, rels, operation=operation,
                                        metadata=metadata)

tests/test-strip.t

@@ -1246,7 +1246,7 b' Test high-level scmutil.cleanupnodes API'
   >                            node(b'D'): [node(b'D2')],
   >                            node(b'G'): [node(b'G2')]}
   >                 scmutil.cleanupnodes(repo, mapping, b'replace')
-  >                 scmutil.cleanupnodes(repo, nodes(b'((B::)+I+Z)-D2'),
+  >                 scmutil.cleanupnodes(repo, nodes(b'((B::)+I+Z)-D2-obsolete()'),
   >                                      b'replace')
   > EOF
   $ hg testnodescleanup --config extensions.t=$TESTTMP/scmutilcleanup.py