corrupt branch resetting (but not yet reflog walking)

Git/RecoverRepository.hs

@@ -169,11 +169,40 @@ copyObjects srcr destr = rsync
 
 {- To deal with missing objects that cannot be recovered, resets any
  - local branches to point to an old commit before the missing
- - objects.
+ - objects. Returns all branches that were changed, and deleted.
  -}
-resetLocalBranches :: MissingObjects -> GoodCommits -> Repo -> IO [Branch]
-resetLocalBranches missing goodcommits r = do
-	error "TODO"
+resetLocalBranches :: MissingObjects -> GoodCommits -> Repo -> IO ([Branch], [Branch], GoodCommits)
+resetLocalBranches missing goodcommits r =
+	go [] [] goodcommits =<< filter islocalbranch <$> getAllRefs r
+  where
+	islocalbranch b = "refs/heads/" `isPrefixOf` show b
+	go changed deleted gcs [] = return (changed, deleted, gcs)
+	go changed deleted gcs (b:bs) = do
+		(mc, gcs') <- findUncorruptedCommit missing gcs b r
+		case mc of
+			Just c
+				| c == b -> go changed deleted gcs' bs
+				| otherwise -> do
+					reset b c
+					go (b:changed) deleted gcs' bs
+			Nothing -> do
+				(mc', gcs'') <- findOldBranch missing gcs' b r
+				case mc' of
+					Just c
+						| c == b -> go changed deleted gcs' bs
+						| otherwise -> do
+							reset b c
+							go (b:changed) deleted gcs'' bs
+					Nothing -> do
+						nukeBranchRef b r
+						go changed (b:deleted) gcs'' bs
+	reset b c = do
+		nukeBranchRef b	r
+		void $ runBool
+			[ Param "branch"
+			, Param (show $ Ref.base b)
+			, Param (show c)
+			] r
 
 {- To deal with missing objects that cannot be recovered, removes
  - any remote tracking branches that reference them. Returns a list of
@@ -255,6 +284,7 @@ findUncorruptedCommit missing goodcommits branch r = do
 		else do
 			(ls, cleanup) <- pipeNullSplit
 				[ Param "log"
+				, Param "-z"
 				, Param "--format=%H"
 				, Param (show branch)
 				] r
@@ -284,11 +314,12 @@ verifyCommit missing goodcommits commit r
 	| otherwise = do
 		(ls, cleanup) <- pipeNullSplit
 			[ Param "log"
+			, Param "-z"
 			, Param "--format=%H %T"
 			, Param (show commit)
 			] r
 		let committrees = map parse ls
-		if any isNothing committrees
+		if any isNothing committrees || null committrees
 			then do
 				void cleanup
 				return (False, goodcommits)
@@ -304,7 +335,7 @@ verifyCommit missing goodcommits commit r
 			<$> extractSha commitsha
 			<*> extractSha treesha
 		_ -> Nothing
-	check [] = return False
+	check [] = return True
 	check ((commit, tree):rest)
 		| checkGoodCommit commit goodcommits = return True
 		| otherwise = verifyTree missing tree r <&&> check rest

doc/design/assistant/disaster_recovery.mdwn

@@ -143,8 +143,7 @@ that was found for it.
   `git annex fsck --fast` to fix up any object location info.
 * Remote tracking branches can just be removed, and then `git fetch`
   from the remote, which will re-download missing objects from it and
-  reinstate the tracking branch.
-* For other branches (or tags), it's best to not rewrite them, because
-  that could get really confusing. Instead, delete the old broken branch,
-  and make a "recovered/$branch" that holds the last good commit (if one
-  was found).
+  reinstate the tracking branch. **done**
+* For other branches, reset them to last good commit, or delete
+  if none was found.
+* (Decided not to touch tags.)

git-recover-repository.hs

@@ -16,6 +16,7 @@ import Common
 import qualified Git.CurrentRepo
 import qualified Git.RecoverRepository
 import qualified Git.Config
+import qualified Git.Branch
 
 header :: String
 header = "Usage: git-recover-repository"
@@ -34,7 +35,7 @@ parseArgs = do
 enableDebugOutput :: IO ()
 enableDebugOutput = do
 	s <- setFormatter
-		<$> streamHandler stderr NOTICE
+		<$> streamHandler stderr DEBUG -- NOTICE
 		<*> pure (simpleLogFormatter "$msg")
 	updateGlobalLogger rootLoggerName (setLevel DEBUG . setHandlers [s])
 
@@ -66,8 +67,20 @@ main = do
 							, show (length remotebranches)
 							, "remote tracking branches that referred to missing objects"
 							]
-					localbranches <- Git.RecoverRepository.resetLocalBranches stillmissing goodcommits g
-					unless (null localbranches) $ do
+					(resetbranches, deletedbranches, _) <- Git.RecoverRepository.resetLocalBranches stillmissing goodcommits g
+					unless (null resetbranches) $ do
 						putStrLn "Reset these local branches to old versions before the missing objects were committed:"
-						putStr $ unlines $ map show localbranches
+						putStr $ unlines $ map show resetbranches
+					unless (null deletedbranches) $ do
+						putStrLn "Deleted these local branches, which could not be recovered due to missing objects:"
+						putStr $ unlines $ map show deletedbranches
+					mcurr <- Git.Branch.currentUnsafe g
+					case mcurr of
+						Nothing -> return ()
+						Just curr -> when (any (== curr) (resetbranches ++ deletedbranches)) $ do
+							putStrLn $ unwords
+								[ "You currently have"
+								, show curr
+								, "checked out. You may have staged changes in the index that can be committed to recover the lost state of this branch!"
+								]
 				else putStrLn "To force a recovery to a usable state, run this command again with the --force parameter."