migrate: --force will force migration of keys already using the destination backend. Useful in rare cases.

Command/Migrate.hs

@@ -16,6 +16,7 @@ import Types.KeySource
 import Annex.Content
 import qualified Command.ReKey
 import qualified Command.Fsck
+import qualified Annex
 
 cmd :: [Command]
 cmd = [notDirect $ withOptions annexedMatchingOptions $
@@ -27,13 +28,14 @@ seek = withFilesInGit $ whenAnnexed start
 
 start :: FilePath -> Key -> CommandStart
 start file key = do
+	forced <- Annex.getState Annex.force
 	v <- Backend.getBackend file key
 	case v of
 		Nothing -> stop
 		Just oldbackend -> do
 			exists <- inAnnex key
 			newbackend <- choosebackend =<< chooseBackend file
-			if (newbackend /= oldbackend || upgradableKey oldbackend key) && exists
+			if (newbackend /= oldbackend || upgradableKey oldbackend key || forced) && exists
 				then do
 					showStart "migrate" file
 					next $ perform file key oldbackend newbackend

debian/changelog

@@ -5,6 +5,8 @@ git-annex (5.20150318) UNRELEASED; urgency=medium
     to be present on a remote.
   * Added a post-update-annex hook, which is run after the git-annex branch
     is updated. Needed for git update-server-info.
+  * migrate: --force will force migration of keys already using the
+    destination backend. Useful in rare cases.
 
  -- Joey Hess <id@joeyh.name>  Thu, 19 Mar 2015 17:05:32 -0400
 

doc/git-annex.mdwn

@@ -868,6 +868,7 @@ subdirectories).
   Normally, nothing will be done to files already using the new backend.
   However, if a backend changes the information it uses to construct a key,
   this can also be used to migrate files to use the new key format.
+  (To force migration of keys already using the new backend, use --force.)
 
 * `reinject src dest`