doctor: skip unknown visibleheads format

Summary:
When I run `hg doctor` in my www checkout it fails the assertion check of the
first line of visibleheads is "v1". Make it graceful so doctor can check and
fix other components.

Reviewed By: DurhamG

Differential Revision: D20147969

fbshipit-source-id: 6aee2cab962fcd0ef06a0611d288021e86621249

eden/scm/edenscm/mercurial/commands/doctor.py

@@ -239,7 +239,10 @@ def repairvisibleheads(ui, metalog, cl):
     """Attempt to fix visibleheads by removing invalid commit hashes"""
     oldtext = decodeutf8(metalog.get("visibleheads") or b"")
     oldlines = oldtext.splitlines()
-    assert oldlines[0] == "v1"
+    # Only support v1 right now.
+    if oldlines[0:1] != ["v1"]:
+        ui.write_err(_("visibleheads: skipped\n"))
+        return
     nodemap = cl.nodemap
     newlines = [oldlines[0]] + [
         hexnode

eden/scm/tests/test-doctor.t

@@ -119,6 +119,23 @@ Check changelog repiar:
 
   $ hg status
 
+Check unknown visibleheads format:
+
+  $ newrepo
+  $ hg dbsh << 'EOS'
+  > ml = repo.svfs.metalog
+  > ml.set("visibleheads", "v-1")
+  > ml.commit("break visibleheads")
+  > EOS
+  $ hg doctor
+  checking internal storage
+  mutation: looks okay
+  changelog: looks okay
+  metalog: looks okay
+  visibleheads: skipped
+  treestate: looks okay
+  allheads: looks okay
+
 Check dirstate pointing to a stripped commit:
 
   $ newrepo
@@ -203,4 +220,14 @@ Try other kinds of dirstate corruptions:
   visibleheads: looks okay
   treestate: repaired
   allheads: looks okay
+  $ hg status
+  M A2
+  A A0
+  A X
+  R A
+  R A1
+  ? B
+  ? C
+  ? Y
+  ? Z
 #endif