318 lines
10 KiB
Haskell
318 lines
10 KiB
Haskell
{- management of the git-annex branch
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-
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- Copyright 2011 Joey Hess <joey@kitenet.net>
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-
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- Licensed under the GNU GPL version 3 or higher.
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-}
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module Annex.Branch (
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name,
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hasOrigin,
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hasSibling,
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siblingBranches,
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create,
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update,
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forceUpdate,
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updateTo,
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get,
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change,
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commit,
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files,
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) where
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import qualified Data.ByteString.Lazy.Char8 as L
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import Common.Annex
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import Annex.Exception
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import Annex.BranchState
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import Annex.Journal
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import qualified Git
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import qualified Git.Command
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import qualified Git.Ref
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import qualified Git.Branch
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import qualified Git.UnionMerge
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import qualified Git.HashObject
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import qualified Git.Index
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import Annex.CatFile
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{- Name of the branch that is used to store git-annex's information. -}
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name :: Git.Ref
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name = Git.Ref "git-annex"
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{- Fully qualified name of the branch. -}
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fullname :: Git.Ref
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fullname = Git.Ref $ "refs/heads/" ++ show name
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{- Branch's name in origin. -}
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originname :: Git.Ref
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originname = Git.Ref $ "origin/" ++ show name
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{- Does origin/git-annex exist? -}
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hasOrigin :: Annex Bool
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hasOrigin = inRepo $ Git.Ref.exists originname
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{- Does the git-annex branch or a sibling foo/git-annex branch exist? -}
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hasSibling :: Annex Bool
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hasSibling = not . null <$> siblingBranches
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{- List of git-annex (refs, branches), including the main one and any
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- from remotes. Duplicate refs are filtered out. -}
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siblingBranches :: Annex [(Git.Ref, Git.Branch)]
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siblingBranches = inRepo $ Git.Ref.matchingUniq name
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{- Creates the branch, if it does not already exist. -}
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create :: Annex ()
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create = do
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_ <- getBranch
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return ()
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{- Returns the ref of the branch, creating it first if necessary. -}
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getBranch :: Annex (Git.Ref)
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getBranch = maybe (hasOrigin >>= go >>= use) (return) =<< branchsha
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where
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go True = do
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inRepo $ Git.Command.run "branch"
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[Param $ show name, Param $ show originname]
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fromMaybe (error $ "failed to create " ++ show name)
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<$> branchsha
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go False = withIndex' True $ do
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inRepo $ Git.Branch.commit "branch created" fullname []
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use sha = do
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setIndexSha sha
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return sha
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branchsha = inRepo $ Git.Ref.sha fullname
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{- Ensures that the branch and index are is up-to-date; should be
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- called before data is read from it. Runs only once per git-annex run.
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-}
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update :: Annex ()
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update = runUpdateOnce $ updateTo =<< siblingBranches
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{- Forces an update even if one has already been run. -}
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forceUpdate :: Annex ()
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forceUpdate = updateTo =<< siblingBranches
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{- Merges the specified Refs into the index, if they have any changes not
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- already in it. The Branch names are only used in the commit message;
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- it's even possible that the provided Branches have not been updated to
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- point to the Refs yet.
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-
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- Before refs are merged into the index, it's important to first stage the
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- journal into the index. Otherwise, any changes in the journal would
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- later get staged, and might overwrite changes made during the merge.
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- If no Refs are provided, the journal is still staged and committed.
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-
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- (It would be cleaner to handle the merge by updating the journal, not the
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- index, with changes from the branches.)
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-
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- The branch is fast-forwarded if possible, otherwise a merge commit is
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- made.
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-}
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updateTo :: [(Git.Ref, Git.Branch)] -> Annex ()
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updateTo pairs = do
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-- ensure branch exists, and get its current ref
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branchref <- getBranch
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-- check what needs updating before taking the lock
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dirty <- journalDirty
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(refs, branches) <- unzip <$> filterM isnewer pairs
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if (not dirty && null refs)
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then updateIndex branchref
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else withIndex $ lockJournal $ do
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when dirty stageJournal
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let merge_desc = if null branches
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then "update"
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else "merging " ++
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unwords (map Git.Ref.describe branches) ++
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" into " ++ show name
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unless (null branches) $ do
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showSideAction merge_desc
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mergeIndex refs
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ff <- if dirty
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then return False
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else inRepo $ Git.Branch.fastForward fullname refs
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if ff
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then updateIndex branchref
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else commitBranch branchref merge_desc
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(nub $ fullname:refs)
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invalidateCache
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where
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isnewer (r, _) = inRepo $ Git.Branch.changed fullname r
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{- Gets the content of a file on the branch, or content from the journal, or
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- staged in the index.
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-
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- Returns an empty string if the file doesn't exist yet. -}
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get :: FilePath -> Annex String
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get = get' False
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{- Like get, but does not merge the branch, so the info returned may not
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- reflect changes in remotes. (Changing the value this returns, and then
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- merging is always the same as using get, and then changing its value.) -}
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getStale :: FilePath -> Annex String
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getStale = get' True
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get' :: Bool -> FilePath -> Annex String
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get' staleok file = fromcache =<< getCache file
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where
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fromcache (Just content) = return content
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fromcache Nothing = fromjournal =<< getJournalFile file
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fromjournal (Just content) = cache content
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fromjournal Nothing
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| staleok = withIndex frombranch
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| otherwise = withIndexUpdate $ frombranch >>= cache
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frombranch = L.unpack <$> catFile fullname file
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cache content = do
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setCache file content
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return content
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{- Applies a function to modifiy the content of a file.
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-
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- Note that this does not cause the branch to be merged, it only
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- modifes the current content of the file on the branch.
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-}
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change :: FilePath -> (String -> String) -> Annex ()
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change file a = lockJournal $ getStale file >>= return . a >>= set file
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{- Records new content of a file into the journal and cache. -}
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set :: FilePath -> String -> Annex ()
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set file content = do
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setJournalFile file content
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setCache file content
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{- Stages the journal, and commits staged changes to the branch. -}
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commit :: String -> Annex ()
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commit message = whenM journalDirty $ lockJournal $ do
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stageJournal
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ref <- getBranch
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withIndex $ commitBranch ref message [fullname]
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{- Commits the staged changes in the index to the branch.
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-
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- Ensures that the branch's index file is first updated to the state
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- of the brannch at branchref, before running the commit action. This
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- is needed because the branch may have had changes pushed to it, that
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- are not yet reflected in the index.
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-
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- Also safely handles a race that can occur if a change is being pushed
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- into the branch at the same time. When the race happens, the commit will
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- be made on top of the newly pushed change, but without the index file
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- being updated to include it. The result is that the newly pushed
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- change is reverted. This race is detected and another commit made
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- to fix it.
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-
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- The branchref value can have been obtained using getBranch at any
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- previous point, though getting it a long time ago makes the race
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- more likely to occur.
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-}
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commitBranch :: Git.Ref -> String -> [Git.Ref] -> Annex ()
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commitBranch branchref message parents = do
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updateIndex branchref
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committedref <- inRepo $ Git.Branch.commit message fullname parents
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setIndexSha committedref
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parentrefs <- commitparents <$> catObject committedref
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when (racedetected branchref parentrefs) $
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fixrace committedref parentrefs
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where
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-- look for "parent ref" lines and return the refs
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commitparents = map (Git.Ref . snd) . filter isparent .
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map (toassoc . L.unpack) . L.lines
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toassoc = separate (== ' ')
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isparent (k,_) = k == "parent"
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{- The race can be detected by checking the commit's
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- parent, which will be the newly pushed branch,
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- instead of the expected ref that the index was updated to. -}
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racedetected expectedref parentrefs
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| expectedref `elem` parentrefs = False -- good parent
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| otherwise = True -- race!
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{- To recover from the race, union merge the lost refs
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- into the index, and recommit on top of the bad commit. -}
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fixrace committedref lostrefs = do
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mergeIndex lostrefs
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commitBranch committedref racemessage [committedref]
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racemessage = message ++ " (recovery from race)"
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{- Lists all files on the branch. There may be duplicates in the list. -}
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files :: Annex [FilePath]
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files = withIndexUpdate $ do
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bfiles <- inRepo $ Git.Command.pipeNullSplit
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[Params "ls-tree --name-only -r -z", Param $ show fullname]
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jfiles <- getJournalledFiles
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return $ jfiles ++ bfiles
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{- Populates the branch's index file with the current branch contents.
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-
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- This is only done when the index doesn't yet exist, and the index
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- is used to build up changes to be commited to the branch, and merge
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- in changes from other branches.
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-}
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genIndex :: Git.Repo -> IO ()
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genIndex g = Git.UnionMerge.stream_update_index g
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[Git.UnionMerge.ls_tree fullname g]
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{- Merges the specified refs into the index.
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- Any changes staged in the index will be preserved. -}
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mergeIndex :: [Git.Ref] -> Annex ()
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mergeIndex branches = do
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h <- catFileHandle
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inRepo $ \g -> Git.UnionMerge.merge_index h g branches
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{- Runs an action using the branch's index file. -}
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withIndex :: Annex a -> Annex a
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withIndex = withIndex' False
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withIndex' :: Bool -> Annex a -> Annex a
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withIndex' bootstrapping a = do
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f <- fromRepo gitAnnexIndex
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bracketIO (Git.Index.override f) id $ do
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unlessM (liftIO $ doesFileExist f) $ do
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unless bootstrapping create
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liftIO $ createDirectoryIfMissing True $ takeDirectory f
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unless bootstrapping $ inRepo genIndex
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a
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{- Runs an action using the branch's index file, first making sure that
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- the branch and index are up-to-date. -}
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withIndexUpdate :: Annex a -> Annex a
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withIndexUpdate a = update >> withIndex a
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{- Updates the branch's index to reflect the current contents of the branch.
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- Any changes staged in the index will be preserved.
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-
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- Compares the ref stored in the lock file with the current
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- ref of the branch to see if an update is needed.
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-}
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updateIndex :: Git.Ref -> Annex ()
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updateIndex branchref = do
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lock <- fromRepo gitAnnexIndexLock
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lockref <- Git.Ref . firstLine <$>
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liftIO (catchDefaultIO (readFileStrict lock) "")
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when (lockref /= branchref) $ do
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withIndex $ mergeIndex [fullname]
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setIndexSha branchref
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{- Record that the branch's index has been updated to correspond to a
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- given ref of the branch. -}
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setIndexSha :: Git.Ref -> Annex ()
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setIndexSha ref = do
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lock <- fromRepo gitAnnexIndexLock
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liftIO $ writeFile lock $ show ref ++ "\n"
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{- Stages the journal into the index. -}
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stageJournal :: Annex ()
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stageJournal = do
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fs <- getJournalFiles
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g <- gitRepo
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withIndex $ liftIO $ do
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let dir = gitAnnexJournalDir g
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let paths = map (dir </>) fs
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(shas, cleanup) <- Git.HashObject.hashFiles paths g
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Git.UnionMerge.update_index g $
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index_lines shas (map fileJournal fs)
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cleanup
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mapM_ removeFile paths
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where
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index_lines shas = map genline . zip shas
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genline (sha, file) = Git.UnionMerge.update_index_line sha file
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