git-annex adjust --lock-missing

Like --hide-missing the branch does not get updated when content
availability changes.

Seems to basically work, but sync does not update it yet.

Also, when a file is present and so unlocked, git mv followed by
git-annex sync results in the basis branch being updated to contain the
file with the new name, unlocked. This seems different than what
happens in an adjusted unlocked branch, where the commit propigates back
locked. Probably the reverse adjustment code needs to be improved to
handle this case.

Annex/AdjustedBranch/Name.hs

@@ -1,6 +1,6 @@
 {- adjusted branch names
  -
- - Copyright 2016-2018 Joey Hess <id@joeyh.name>
+ - Copyright 2016-2020 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -37,12 +37,16 @@ instance SerializeAdjustment Adjustment where
 		serializeAdjustment p
 	serializeAdjustment (PresenceAdjustment p (Just l)) = 
 		serializeAdjustment p <> "-" <> serializeAdjustment l
+	serializeAdjustment (LinkMissingAdjustment l) =
+		serializeAdjustment l
 	deserializeAdjustment s = 
 		(LinkAdjustment <$> deserializeAdjustment s)
 			<|>
 		(PresenceAdjustment <$> deserializeAdjustment s1 <*> pure (deserializeAdjustment s2))
 			<|>
 		(PresenceAdjustment <$> deserializeAdjustment s <*> pure Nothing)
+			<|>
+		(LinkMissingAdjustment <$> deserializeAdjustment s)
 	  where
 		(s1, s2) = separate' (== (fromIntegral (ord '-'))) s
 
@@ -64,6 +68,13 @@ instance SerializeAdjustment PresenceAdjustment where
 	deserializeAdjustment "showmissing" = Just ShowMissingAdjustment
 	deserializeAdjustment _ = Nothing
 
+instance SerializeAdjustment LinkMissingAdjustment where
+	serializeAdjustment LockMissingAdjustment = "lockmissing"
+	serializeAdjustment UnlockMissingAdjustment = "unlockmissing"
+	deserializeAdjustment "lockmissing" = Just LockMissingAdjustment
+	deserializeAdjustment "unlockmissing" = Just UnlockMissingAdjustment
+	deserializeAdjustment _ = Nothing
+
 newtype AdjBranch = AdjBranch { adjBranch :: Branch }
 
 originalToAdjusted :: OrigBranch -> Adjustment -> AdjBranch