diff --git a/edenscm/mercurial/commands/__init__.py b/edenscm/mercurial/commands/__init__.py
index c565e80798..30aadc9e3a 100644
--- a/edenscm/mercurial/commands/__init__.py
+++ b/edenscm/mercurial/commands/__init__.py
@@ -20,6 +20,7 @@ import time
 from . import (
     debug,
     debugcheckoutidentifier,
+    debugmutation,
     debugstatus,
     debugstrip,
     eden,
@@ -81,6 +82,7 @@ readonly = registrar.command.readonly
 
 table.update(uncommit.cmdtable)
 table.update(debugcheckoutidentifier.command._table)
+table.update(debugmutation.command._table)
 table.update(debugstatus.command._table)
 table.update(debugstrip.command._table)
 table.update(eden.command._table)
diff --git a/edenscm/mercurial/commands/debug.py b/edenscm/mercurial/commands/debug.py
index ee9001c270..bc40c5cafc 100644
--- a/edenscm/mercurial/commands/debug.py
+++ b/edenscm/mercurial/commands/debug.py
@@ -3289,45 +3289,3 @@ def debugtreestate(ui, repo, cmd="status", **opts):
             )
     else:
         raise error.Abort("unrecognised command: %s" % cmd)
-
-
-@command(b"debugmutation", [], _("[REV]"))
-def debugmutation(ui, repo, *revs, **opts):
-    """display the mutation history of a commit"""
-    repo = repo.unfiltered()
-    opts = pycompat.byteskwargs(opts)
-    for rev in scmutil.revrange(repo, revs):
-        ctx = repo[rev]
-        nodestack = [[ctx.node()]]
-        while nodestack:
-            node = nodestack[-1].pop()
-            ui.status(("%s%s") % ("  " * len(nodestack), hex(node)))
-            entry = mutation.lookup(repo, node)
-            if entry is not None:
-                preds = entry.preds()
-                mutop = entry.op()
-                mutuser = entry.user()
-                mutdate = util.shortdatetime((entry.time(), entry.tz()))
-                mutsplit = entry.split() or None
-                origin = entry.origin()
-                origin = {
-                    None: "",
-                    mutation.ORIGIN_LOCAL: "",
-                    mutation.ORIGIN_COMMIT: " (from remote commit)",
-                    mutation.ORIGIN_OBSMARKER: " (from obsmarker)",
-                    mutation.ORIGIN_SYNTHETIC: " (synthetic)",
-                }.get(origin, " (unknown origin %s)" % origin)
-                extra = ""
-                if mutsplit is not None:
-                    extra += " (split into this and: %s)" % ", ".join(
-                        [hex(n) for n in mutsplit]
-                    )
-                ui.status(
-                    (" %s by %s at %s%s%s from:")
-                    % (mutop, mutuser, mutdate, extra, origin)
-                )
-                nodestack.append(list(reversed(preds)))
-            ui.status(("\n"))
-            while nodestack and not nodestack[-1]:
-                nodestack.pop()
-    return 0
diff --git a/edenscm/mercurial/commands/debugmutation.py b/edenscm/mercurial/commands/debugmutation.py
new file mode 100644
index 0000000000..7a16092c7e
--- /dev/null
+++ b/edenscm/mercurial/commands/debugmutation.py
@@ -0,0 +1,185 @@
+# debugmutation.py - command processing for debugmutation* commands
+#
+# Copyright 2019 Facebook, Inc.
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+from __future__ import absolute_import
+
+from .. import mutation, node as nodemod, pycompat, registrar, scmutil, util
+from ..i18n import _
+
+
+command = registrar.command()
+
+
+@command(b"debugmutation", [], _("[REV]"))
+def debugmutation(ui, repo, *revs, **opts):
+    """display the mutation history of a commit"""
+    repo = repo.unfiltered()
+    opts = pycompat.byteskwargs(opts)
+    for rev in scmutil.revrange(repo, revs):
+        ctx = repo[rev]
+        nodestack = [[ctx.node()]]
+        while nodestack:
+            node = nodestack[-1].pop()
+            ui.status(("%s%s") % ("  " * len(nodestack), nodemod.hex(node)))
+            entry = mutation.lookup(repo, node)
+            if entry is not None:
+                preds = entry.preds()
+                mutop = entry.op()
+                mutuser = entry.user()
+                mutdate = util.shortdatetime((entry.time(), entry.tz()))
+                mutsplit = entry.split() or None
+                origin = entry.origin()
+                origin = {
+                    None: "",
+                    mutation.ORIGIN_LOCAL: "",
+                    mutation.ORIGIN_COMMIT: " (from remote commit)",
+                    mutation.ORIGIN_OBSMARKER: " (from obsmarker)",
+                    mutation.ORIGIN_SYNTHETIC: " (synthetic)",
+                }.get(origin, " (unknown origin %s)" % origin)
+                extra = ""
+                if mutsplit is not None:
+                    extra += " (split into this and: %s)" % ", ".join(
+                        [nodemod.hex(n) for n in mutsplit]
+                    )
+                ui.status(
+                    (" %s by %s at %s%s%s from:")
+                    % (mutop, mutuser, mutdate, extra, origin)
+                )
+                nodestack.append(list(reversed(preds)))
+            ui.status(("\n"))
+            while nodestack and not nodestack[-1]:
+                nodestack.pop()
+    return 0
+
+
+@command(b"debugmutationfromobsmarkers", [])
+def debugmutationfromobsmarkers(ui, repo, **opts):
+    """convert obsolescence markers to mutation records"""
+    obsmarkers = repo.obsstore._all
+    # Sort obsmarkers by date.  Applying them in probable date order gives us
+    # a better chance of resolving cycles in the right way.
+    obsmarkers.sort(key=lambda x: x[4])
+    newmut = {}
+
+    def checkloopfree(pred, succs):
+        candidates = {pred}
+        while candidates:
+            candidate = candidates.pop()
+            if candidate in newmut:
+                mutpreds, mutsplit, _markers = newmut[candidate]
+                for succ in succs:
+                    if succ in mutpreds:
+                        repo.ui.debug(
+                            "ignoring loop: %s -> %s\n  history loops at %s -> %s\n"
+                            % (
+                                nodemod.hex(pred),
+                                ", ".join([nodemod.hex(s) for s in succs]),
+                                nodemod.hex(succ),
+                                nodemod.hex(candidate),
+                            )
+                        )
+                        return False
+                candidates.update(mutpreds)
+        return True
+
+    dropprune = 0
+    droprevive = 0
+    dropundo = 0
+    droploop = 0
+    dropinvalid = 0
+
+    for obsmarker in obsmarkers:
+        obspred, obssuccs, obsflag, obsmeta, obsdate, obsparents = obsmarker
+        if not obssuccs:
+            # Skip prune markers
+            dropprune += 1
+            continue
+        if obssuccs == (obspred,):
+            # Skip revive markers
+            droprevive += 1
+            continue
+        obsmeta = dict(obsmeta)
+        if obsmeta.get("operation") in ("undo", "uncommit", "unamend"):
+            # Skip undo-style markers
+            dropundo += 1
+            continue
+        if not checkloopfree(obspred, obssuccs):
+            # Skip markers that introduce loops
+            droploop += 1
+            continue
+        if len(obssuccs) > 1:
+            # Split marker
+            succ = obssuccs[-1]
+            if succ in newmut:
+                preds, split, markers = newmut[succ]
+                if obsmarker in markers:
+                    # duplicate
+                    continue
+                repo.ui.debug(
+                    "invalid obsmarker found: %s -> %s is both split and folded\n"
+                    % (nodemod.hex(obspred), nodemod.hex(succ))
+                )
+                dropinvalid += 1
+                continue
+            newmut[succ] = ([obspred], obssuccs[:-1], [obsmarker])
+        elif obssuccs[0] in newmut:
+            preds, split, markers = newmut[obssuccs[0]]
+            if obsmarker in markers:
+                # duplicate
+                continue
+            # Fold marker
+            preds.append(obspred)
+            markers.append(obsmarker)
+        else:
+            # Normal marker
+            newmut[obssuccs[0]] = ([obspred], None, [obsmarker])
+
+    repo.ui.debug(
+        "dropped markers: prune: %s, revive: %s, undo: %s, loop: %s, invalid: %s\n"
+        % (dropprune, droprevive, dropundo, droploop, dropinvalid)
+    )
+
+    entries = []
+
+    for succ, (preds, split, obsmarkers) in newmut.items():
+        if mutation.lookup(repo, succ) is not None:
+            # Have already converted this successor, or already know about it
+            continue
+        mutop = ""
+        mutuser = ""
+        mutdate = None
+        for obsmarker in obsmarkers:
+            obspred, obssuccs, obsflag, obsmeta, obsdate, obsparents = obsmarker
+            obsmeta = dict(obsmeta)
+            obsop = obsmeta.get("operation", "")
+            if not mutop or obsop not in ("", "copy"):
+                mutop = obsop
+            obsuser = obsmeta.get("user", "")
+            if not mutuser and obsuser:
+                mutuser = obsuser
+            if not mutdate:
+                mutdate = obsdate
+
+        entries.append(
+            mutation.createsyntheticentry(
+                repo,
+                mutation.ORIGIN_OBSMARKER,
+                preds,
+                succ,
+                mutop,
+                split,
+                mutuser,
+                mutdate,
+            )
+        )
+
+    repo.ui.write(
+        _("generated %s entries for %s commits\n") % (len(entries), len(newmut))
+    )
+    with repo.lock():
+        count = mutation.recordentries(repo, entries, skipexisting=False)
+        repo.ui.write(_("wrote %s entries\n") % count)
diff --git a/edenscm/mercurial/mutation.py b/edenscm/mercurial/mutation.py
index 2eb5dddcbf..75b47933aa 100644
--- a/edenscm/mercurial/mutation.py
+++ b/edenscm/mercurial/mutation.py
@@ -127,6 +127,7 @@ def createcommitentry(repo, node):
 
 
 def recordentries(repo, entries, skipexisting=True):
+    count = 0
     with repo.transaction("record-mutation") as tr:
         unfi = repo.unfiltered()
         ms = repo._mutationstore
@@ -137,6 +138,8 @@ def recordentries(repo, entries, skipexisting=True):
                 if succ in unfi or ms.has(succ):
                     continue
             ms.add(entry)
+            count += 1
+    return count
 
 
 def lookup(repo, node, extra=None):
diff --git a/tests/test-completion.t b/tests/test-completion.t
index a755ff5127..fa300f4289 100644
--- a/tests/test-completion.t
+++ b/tests/test-completion.t
@@ -112,6 +112,7 @@ Show debug commands if there are no other candidates
   debuglocks
   debugmergestate
   debugmutation
+  debugmutationfromobsmarkers
   debugnamecomplete
   debugobsolete
   debugpathcomplete
@@ -306,6 +307,7 @@ Show all commands + options
   debuglocks: force-lock, force-wlock, force-undolog-lock, set-lock, set-wlock
   debugmergestate: 
   debugmutation: 
+  debugmutationfromobsmarkers: 
   debugnamecomplete: 
   debugobsolete: flags, record-parents, rev, exclusive, index, delete, date, user, template
   debugpathcomplete: full, normal, added, removed
diff --git a/tests/test-help.t b/tests/test-help.t
index 1d899ba310..f8805e1917 100644
--- a/tests/test-help.t
+++ b/tests/test-help.t
@@ -1004,6 +1004,8 @@ Test list of internal help commands
                  print merge state
    debugmutation
                  display the mutation history of a commit
+   debugmutationfromobsmarkers
+                 convert obsolescence markers to mutation records
    debugnamecomplete
                  complete "names" - tags, open branch names, bookmark names
    debugobsolete