untested transition detection on merging, and transition running code

4 files changed, 142 insertions, 23 deletions

diff --git a/Annex/Branch.hs b/Annex/Branch.hs
index bc3736a9a..fa4b0265d 100644
--- a/Annex/Branch.hs
+++ b/Annex/Branch.hs
@@ -1,6 +1,6 @@
 {- management of the git-annex branch
  -
- - Copyright 2011-2012 Joey Hess <joey@kitenet.net>
+ - Copyright 2011-2013 Joey Hess <joey@kitenet.net>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -22,9 +22,12 @@ module Annex.Branch (
 	commit,
 	files,
 	withIndex,
+	performTransitions,
 ) where
 
 import qualified Data.ByteString.Lazy.Char8 as L
+import qualified Data.Set as S
+import qualified Data.Map as M
 
 import Common.Annex
 import Annex.BranchState
@@ -32,6 +35,7 @@ import Annex.Journal
 import qualified Git
 import qualified Git.Command
 import qualified Git.Ref
+import qualified Git.Sha
 import qualified Git.Branch
 import qualified Git.UnionMerge
 import qualified Git.UpdateIndex
@@ -42,6 +46,8 @@ import Annex.CatFile
 import Annex.Perms
 import qualified Annex
 import Utility.Env
+import Logs.Transitions
+import Annex.ReplaceFile
 
 {- Name of the branch that is used to store git-annex's information. -}
 name :: Git.Ref
@@ -110,6 +116,9 @@ forceUpdate = updateTo =<< siblingBranches
  - later get staged, and might overwrite changes made during the merge.
  - This is only done if some of the Refs do need to be merged.
  -
+ - Also handles performing any Transitions that have not yet been
+ - performed, in either the local branch, or the Refs.
+ -
  - Returns True if any refs were merged in, False otherwise.
  -}
 updateTo :: [(Git.Ref, Git.Branch)] -> Annex Bool
@@ -117,7 +126,8 @@ updateTo pairs = do
 	-- ensure branch exists, and get its current ref
 	branchref <- getBranch
 	dirty <- journalDirty
-	(refs, branches) <- unzip <$> filterM isnewer pairs
+	ignoredrefs <- getIgnoredRefs
+	(refs, branches) <- unzip <$> filterM (isnewer ignoredrefs) pairs
 	if null refs
 		{- Even when no refs need to be merged, the index
 		 - may still be updated if the branch has gotten ahead 
@@ -132,7 +142,9 @@ updateTo pairs = do
 		else lockJournal $ go branchref dirty refs branches
 	return $ not $ null refs
   where
-	isnewer (r, _) = inRepo $ Git.Branch.changed fullname r
+	isnewer ignoredrefs (r, _)
+		| S.member r ignoredrefs = return False
+		| otherwise = inRepo $ Git.Branch.changed fullname r
 	go branchref dirty refs branches = withIndex $ do
 		cleanjournal <- if dirty then stageJournal else return noop
 		let merge_desc = if null branches
@@ -140,16 +152,23 @@ updateTo pairs = do
 			else "merging " ++
 				unwords (map Git.Ref.describe branches) ++ 
 				" into " ++ show name
+		localtransitions <- parseTransitionsStrictly "local"
+			<$> getStale transitionsLog
 		unless (null branches) $ do
 			showSideAction merge_desc
 			mergeIndex refs
-		ff <- if dirty
-			then return False
-			else inRepo $ Git.Branch.fastForward fullname refs
-		if ff
-			then updateIndex branchref
-			else commitBranch branchref merge_desc
-				(nub $ fullname:refs)
+		let commitrefs = nub $ fullname:refs
+		transitioned <- handleTransitions localtransitions commitrefs
+		case transitioned of
+			Nothing -> do
+				ff <- if dirty
+					then return False
+					else inRepo $ Git.Branch.fastForward fullname refs
+				if ff
+					then updateIndex branchref
+					else commitBranch branchref merge_desc commitrefs
+			Just (branchref', commitrefs') ->
+				commitBranch branchref' merge_desc commitrefs'
 		liftIO cleanjournal
 
 {- Gets the content of a file, which may be in the journal, or in the index
@@ -361,3 +380,76 @@ stageJournal = withIndex $ do
 		sha <- hashFile h path
 		streamer $ Git.UpdateIndex.updateIndexLine
 			sha FileBlob (asTopFilePath $ fileJournal file)
+
+{- This is run after the refs have been merged into the index,
+ - but before the result is committed to the branch.
+ - Which is why it's passed the contents of the local branches's
+ - transition log before that merge took place.
+ -
+ - When the refs contain transitions that have not yet been done locally,
+ - the transitions are performed on the index, and a new branch
+ - is created from the result, and returned.
+ -
+ - When there are transitions recorded locally that have not been done
+ - to the remote refs, the transitions are performed in the index,
+ - and the existing branch is returned. In this case, the untransitioned
+ - remote refs cannot be merged into the branch (since transitions
+ - throw away history), so none of them are included in the returned
+ - list of refs, and they are added to the list of refs to ignore,
+ - to avoid re-merging content from them again.
+ -}
+handleTransitions :: Transitions -> [Git.Ref] -> Annex (Maybe (Git.Branch, [Git.Ref]))
+handleTransitions localts refs = do
+	m <- M.fromList <$> mapM getreftransition refs
+	let remotets = M.elems m
+	if all (localts ==) remotets
+		then return Nothing
+		else do
+			let allts = combineTransitions (localts:remotets)
+			let (transitionedrefs, untransitionedrefs) =
+				partition (\r -> M.lookup r m == Just allts) refs
+			transitionedbranch <- performTransitions allts (localts /= allts)
+			ignoreRefs untransitionedrefs
+			return $ Just (transitionedbranch, transitionedrefs)
+  where
+  	getreftransition ref = do
+		ts <- parseTransitionsStrictly "remote" . L.unpack
+			<$> catFile ref transitionsLog
+		return (ref, ts)
+
+ignoreRefs :: [Git.Ref] -> Annex ()
+ignoreRefs rs = do
+	old <- getIgnoredRefs
+	let s = S.unions [old, S.fromList rs]
+	f <- fromRepo gitAnnexIgnoredRefs
+	replaceFile f $ \tmp -> liftIO $ writeFile tmp $
+		unlines $ map show $ S.elems s
+
+getIgnoredRefs :: Annex (S.Set Git.Ref)
+getIgnoredRefs = S.fromList . mapMaybe Git.Sha.extractSha . lines <$> content
+  where
+  	content = do
+		f <- fromRepo gitAnnexIgnoredRefs
+		liftIO $ catchDefaultIO "" $ readFile f
+
+{- Performs the specified transitions on the contents of the index file,
+ - commits it to the branch, or creates a new branch, and returns 
+ - the branch's ref. -}
+performTransitions :: Transitions -> Bool -> Annex Git.Ref
+performTransitions ts neednewbranch = withIndex $ do
+	when (inTransitions ForgetDeadRemotes ts) $
+		error "TODO ForgetDeadRemotes transition"
+	if neednewbranch
+		then do
+			committedref <- inRepo $ Git.Branch.commit message fullname []
+			setIndexSha committedref
+			return committedref
+		else do
+			ref <- getBranch
+			commitBranch ref message [fullname]
+			getBranch
+  where
+  	message
+		| neednewbranch = "new branch for transition " ++ tdesc
+		| otherwise = "continuing transition " ++ tdesc
+	tdesc = show $ map describeTransition $ transitionList ts
diff --git a/Locations.hs b/Locations.hs
index 1cbbb9886..7762afb64 100644
--- a/Locations.hs
+++ b/Locations.hs
@@ -35,6 +35,7 @@ module Locations (
 	gitAnnexJournalLock,
 	gitAnnexIndex,
 	gitAnnexIndexLock,
+	gitAnnexIgnoredRefs,
 	gitAnnexPidFile,
 	gitAnnexDaemonStatusFile,
 	gitAnnexLogFile,
@@ -225,6 +226,10 @@ gitAnnexIndex r = gitAnnexDir r </> "index"
 gitAnnexIndexLock :: Git.Repo -> FilePath
 gitAnnexIndexLock r = gitAnnexDir r </> "index.lck"
 
+{- List of refs that should not be merged into the git-annex branch. -}
+gitAnnexIgnoredRefs :: Git.Repo -> FilePath
+gitAnnexIgnoredRefs r = gitAnnexDir r </> "ignoredrefs"
+
 {- Pid file for daemon mode. -}
 gitAnnexPidFile :: Git.Repo -> FilePath
 gitAnnexPidFile r = gitAnnexDir r </> "daemon.pid"
diff --git a/Logs/Transitions.hs b/Logs/Transitions.hs
index e548a2f23..41f4b2635 100644
--- a/Logs/Transitions.hs
+++ b/Logs/Transitions.hs
@@ -46,6 +46,10 @@ data TransitionLine = TransitionLine
 
 type Transitions = S.Set TransitionLine
 
+describeTransition :: Transition -> String
+describeTransition ForgetGitHistory = "forget git history"
+describeTransition ForgetDeadRemotes = "forget dead remotes"
+
 addTransition :: POSIXTime -> Transition -> Transitions -> Transitions
 addTransition ts t = S.insert $ TransitionLine ts t
 
@@ -60,6 +64,11 @@ parseTransitions = check . map parseTransitionLine . lines
 		| all isJust l = Just $ S.fromList $ catMaybes l
 		| otherwise = Nothing
 
+parseTransitionsStrictly :: String -> String -> Transitions
+parseTransitionsStrictly source = fromMaybe badsource . parseTransitions
+  where
+	badsource = error $ "unknown transitions listed in " ++ source ++ "; upgrade git-annex!"
+
 showTransitionLine :: TransitionLine -> String
 showTransitionLine (TransitionLine ts t) = unwords [show t, show ts]
 
@@ -71,17 +80,14 @@ parseTransitionLine s = TransitionLine <$> pdate ds <*> readish ts
 	ds = unwords $ Prelude.tail ws
 	pdate = parseTime defaultTimeLocale "%s%Qs" >=*> utcTimeToPOSIXSeconds
 
-{- Compares two sets of transitions, and returns a list of any transitions
- - from the second set that have not yet been perfomed in the first,
- - and a list of any transitions from the first set that have not yet been
- - performed in the second. -}
-diffTransitions :: Transitions -> Transitions -> ([Transition], [Transition])
-diffTransitions a b = (b `diff` a, a `diff` b)
-  where
-  	diff x y = map transition $ S.elems $ S.difference x y
+combineTransitions :: [Transitions] -> Transitions
+combineTransitions = S.unions
+
+inTransitions :: Transition -> Transitions -> Bool
+inTransitions t = not . S.null . S.filter (\l -> transition l == t)
 
-sameTransitions :: Transitions -> Transitions -> Bool
-sameTransitions a b = let (x, y) = diffTransitions a b in null x && null y
+transitionList :: Transitions -> [Transition]
+transitionList = map transition . S.elems
 
 {- Typically ran with Annex.Branch.change, but we can't import Annex.Branch
  - here since it depends on this module. -}
@@ -89,6 +95,4 @@ recordTransition :: (FilePath -> (String -> String) -> Annex ()) -> Transition -
 recordTransition changer o = do
 	t <- liftIO getPOSIXTime
 	changer transitionsLog $
-		showTransitions . addTransition t o . fromMaybe badlog . parseTransitions
-  where
-  	badlog = error $ "unknown transitions exist in " ++ transitionsLog
+		showTransitions . addTransition t o . parseTransitionsStrictly "local"
diff --git a/doc/git-annex.mdwn b/doc/git-annex.mdwn
index 7cac9087d..72e376d64 100644
--- a/doc/git-annex.mdwn
+++ b/doc/git-annex.mdwn
@@ -479,6 +479,24 @@ subdirectories).
 
   Upgrades the repository to current layout.
 
+* forget
+
+  Causes the git-annex branch to be rewritten, throwing away historical
+  data about past locations of files, files that are no longer present on
+  any remote, etc. The resulting branch will use less space, but for
+  example `git annex log` will not be able to show where files used to
+  be located.
+  
+  To also prune references to remotes that have been marked as dead,
+  specify --forget-dead.
+
+  When this rewritten branch is merged into other clones of
+  the repository, git-annex will automatically perform the same rewriting
+  to their local git-annex branch. So the forgetfulness will automatically
+  propigate out from its starting point until all repositories running
+  git-annex have forgotten their old history. (You may need to force
+  git to push the branch to any git repositories not running git-annex.
+
 # QUERY COMMANDS
 
 * version