103 lines
3 KiB
Haskell
103 lines
3 KiB
Haskell
{- git branch stuff
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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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{-# LANGUAGE BangPatterns #-}
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module Git.Branch where
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import Common
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import Git
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import Git.Sha
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import Git.Command
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{- The currently checked out branch.
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-
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- In a just initialized git repo before the first commit,
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- symbolic-ref will show the master branch, even though that
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- branch is not created yet. So, this also looks at show-ref HEAD
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- to double-check.
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-}
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current :: Repo -> IO (Maybe Git.Ref)
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current r = do
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v <- currentUnsafe r
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case v of
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Nothing -> return Nothing
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Just branch ->
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ifM (null <$> pipeReadStrict [Param "show-ref", Param $ show branch] r)
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( return Nothing
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, return v
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)
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{- The current branch, which may not really exist yet. -}
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currentUnsafe :: Repo -> IO (Maybe Git.Ref)
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currentUnsafe r = parse . firstLine
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<$> pipeReadStrict [Param "symbolic-ref", Param "HEAD"] r
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where
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parse l
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| null l = Nothing
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| otherwise = Just $ Git.Ref l
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{- Checks if the second branch has any commits not present on the first
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- branch. -}
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changed :: Branch -> Branch -> Repo -> IO Bool
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changed origbranch newbranch repo
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| origbranch == newbranch = return False
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| otherwise = not . null <$> diffs
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where
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diffs = pipeReadStrict
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[ Param "log"
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, Param (show origbranch ++ ".." ++ show newbranch)
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, Params "--oneline -n1"
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] repo
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{- Given a set of refs that are all known to have commits not
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- on the branch, tries to update the branch by a fast-forward.
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-
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- In order for that to be possible, one of the refs must contain
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- every commit present in all the other refs.
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-}
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fastForward :: Branch -> [Ref] -> Repo -> IO Bool
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fastForward _ [] _ = return True
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fastForward branch (first:rest) repo =
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-- First, check that the branch does not contain any
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-- new commits that are not in the first ref. If it does,
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-- cannot fast-forward.
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ifM (changed first branch repo)
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( no_ff
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, maybe no_ff do_ff =<< findbest first rest
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)
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where
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no_ff = return False
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do_ff to = do
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run "update-ref"
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[Param $ show branch, Param $ show to] repo
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return True
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findbest c [] = return $ Just c
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findbest c (r:rs)
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| c == r = findbest c rs
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| otherwise = do
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better <- changed c r repo
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worse <- changed r c repo
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case (better, worse) of
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(True, True) -> return Nothing -- divergent fail
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(True, False) -> findbest r rs -- better
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(False, True) -> findbest c rs -- worse
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(False, False) -> findbest c rs -- same
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{- Commits the index into the specified branch (or other ref),
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- with the specified parent refs, and returns the committed sha -}
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commit :: String -> Branch -> [Ref] -> Repo -> IO Sha
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commit message branch parentrefs repo = do
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tree <- getSha "write-tree" $
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pipeReadStrict [Param "write-tree"] repo
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sha <- getSha "commit-tree" $ pipeWriteRead
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(map Param $ ["commit-tree", show tree] ++ ps)
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message repo
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run "update-ref" [Param $ show branch, Param $ show sha] repo
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return sha
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where
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ps = concatMap (\r -> ["-p", show r]) parentrefs
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