--- a/hgext3rd/evolve/obshistory.py	Tue Apr 21 23:45:11 2020 +0800
+++ b/hgext3rd/evolve/obshistory.py	Thu May 07 01:29:24 2020 +0200
@@ -59,6 +59,7 @@
      (b'a', b'all', False, _(b'show all related changesets, not only precursors')),
      (b'p', b'patch', False, _(b'show the patch between two obs versions')),
      (b'f', b'filternonlocal', False, _(b'filter out non local commits')),
+     (b'o', b'origin', False, _(b'show origin of changesets instead of fate')),
      ] + commands.formatteropts,
     _(b'hg olog [OPTION]... [[-r] REV]...'),
     **compat.helpcategorykwargs('CATEGORY_CHANGE_NAVIGATION'))
@@ -212,18 +213,31 @@
         if not marker[1]:
             yield ((), (marker,))
 
-def _nodesandmarkers(repo, ctx, filternonlocal):
-    if filternonlocal:
-        r = obsutil.successorsandmarkers(repo, ctx)
-        if r is None:
-            r = []
-        for succset in sorted(r):
-            if succset[b'markers']:
-                yield (succset[b'successors'], succset[b'markers'])
+def _nodesandmarkers(repo, ctx, filternonlocal, origin):
+    """ Return data for obslog and obsolescence-related template keywords.
+
+    If `filternonlocal` is True, skip filtered nodes (but still gather
+    obsolescence markers), otherwise the result will contain nodes unknown
+    locally if they are found in the obsolescence markers.
+
+    If `origin` is True, look at predecessors of ctx. Otherwise return
+    successors and appropriate obsmarkers.
+    """
+    if origin:
+        for (nodes, markers) in _originmarkers(repo, ctx, filternonlocal):
+            yield (nodes, markers)
     else:
-        markers = repo.obsstore.successors.get(ctx.node(), ())
-        for marker in sorted(markers):
-            yield (marker[1], [marker])
+        if filternonlocal:
+            r = obsutil.successorsandmarkers(repo, ctx)
+            if r is None:
+                r = []
+            for succset in sorted(r):
+                if succset[b'markers']:
+                    yield (succset[b'successors'], succset[b'markers'])
+        else:
+            markers = repo.obsstore.successors.get(ctx.node(), ())
+            for marker in sorted(markers):
+                yield (marker[1], [marker])
 
 class obsmarker_printer(logcmdutil.changesetprinter):
     """show (available) information about a node
@@ -248,6 +262,7 @@
 
         self.template = diffopts and diffopts.get(b'template')
         self.filter = diffopts and diffopts.get(b'filternonlocal')
+        self.origin = diffopts and diffopts.get(b'origin')
 
     def show(self, ctx, copies=None, matchfn=None, **props):
         if self.buffered:
@@ -262,10 +277,11 @@
 
             markerfm = fm.nested(b"markers")
 
-            data = _nodesandmarkers(self.repo, ctx, self.filter)
+            data = _nodesandmarkers(self.repo, ctx, self.filter, self.origin)
             for nodes, markers in data:
                 displaymarkers(self.ui, markerfm, nodes, markers, ctx.node(),
-                               self.repo, self._includediff)
+                               self.repo, self._includediff,
+                               successive=not self.origin)
 
             markerfm.end()
 
@@ -534,6 +550,7 @@
     seen = set(nodes)
     toshow = []
 
+    origin = opts and opts.get('origin')
     walksuccessors = opts and opts.get('all')
     filternonlocal = opts and opts.get('filternonlocal')
     includediff = opts and opts.get('patch')
@@ -566,10 +583,10 @@
 
         markerfm = fm.nested(b"markers")
 
-        data = _nodesandmarkers(unfi, ctx, filternonlocal)
+        data = _nodesandmarkers(unfi, ctx, filternonlocal, origin)
         for nodes_, markers in data:
             displaymarkers(ui, markerfm, nodes_, markers, ctx.node(), unfi,
-                           includediff)
+                           includediff, successive=not origin)
 
         markerfm.end()