--- a/CHANGELOG	Tue Jul 02 21:00:46 2019 +0530
+++ b/CHANGELOG	Mon Jul 01 19:15:57 2019 +0530
@@ -6,6 +6,7 @@
 
   * pick: no longer forget file in case of conflict (issue6037)
   * pick: properly report and cleanup "unfinished state"
+  * prune: don't update wcp if pruned revision are unrelated (issue6137)
   * evolve: properly prune changeset with no change in case of conflict (issue5967)
 
 9.0.0 -- 2019-06-06

--- a/hgext3rd/evolve/cmdrewrite.py	Tue Jul 02 21:00:46 2019 +0530
+++ b/hgext3rd/evolve/cmdrewrite.py	Mon Jul 01 19:15:57 2019 +0530
@@ -1063,19 +1063,24 @@
 
         wdp = repo['.']
 
-        if len(sucs) == 1 and len(precs) == 1 and wdp in precs:
-            # '.' killed, so update to the successor
-            newnode = sucs[0]
-        elif biject and wdp in precs:
-            # find the exact successor of '.'
-            newnode = sucs[precs.index(wdp)]
+        if wdp in precs:
+            if len(sucs) == 1 and len(precs) == 1:
+                # '.' killed, so update to the successor
+                newnode = sucs[0]
+            elif biject:
+                # find the exact successor of '.'
+                newnode = sucs[precs.index(wdp)]
+            else:
+                # update to an unkilled parent
+                newnode = wdp
+
+                while newnode in precs or newnode.obsolete():
+                    newnode = newnode.parents()[0]
         else:
-            # update to an unkilled parent
+            # no need to update anywhere as wdp is not related to revs
+            # being pruned
             newnode = wdp
 
-            while newnode in precs or newnode.obsolete():
-                newnode = newnode.parents()[0]
-
         if newnode.node() != wdp.node():
             if opts.get('keep', False):
                 # This is largely the same as the implementation in

--- a/tests/test-prune.t	Tue Jul 02 21:00:46 2019 +0530
+++ b/tests/test-prune.t	Mon Jul 01 19:15:57 2019 +0530
@@ -493,12 +493,11 @@
   o  0:9092f1db7931[] (draft) added a
   
   $ hg prune -r "desc('added c')"
-  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
-  working directory is now at 9092f1db7931
   1 changesets pruned
 
   $ hg par
-  0:9092f1db7931[] (draft) added a
-XXX: it doesn't make sense to update to "added a"; parent should be "added b"
+  1:5f6d8a4bf34a[] (obsolete/draft) added b
+  working directory parent is obsolete! (5f6d8a4bf34a)
+  (use 'hg evolve' to update to its parent successor)
 
   $ cd ..