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|
{- git branch stuff
-
- Copyright 2011 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
{-# LANGUAGE BangPatterns #-}
module Git.Branch where
import Common
import Git
import Git.Sha
import Git.Command
{- The currently checked out branch.
-
- In a just initialized git repo before the first commit,
- symbolic-ref will show the master branch, even though that
- branch is not created yet. So, this also looks at show-ref HEAD
- to double-check.
-}
current :: Repo -> IO (Maybe Git.Ref)
current r = do
v <- currentUnsafe r
case v of
Nothing -> return Nothing
Just branch ->
ifM (null <$> pipeReadStrict [Param "show-ref", Param $ show branch] r)
( return Nothing
, return v
)
{- The current branch, which may not really exist yet. -}
currentUnsafe :: Repo -> IO (Maybe Git.Ref)
currentUnsafe r = parse . firstLine
<$> pipeReadStrict [Param "symbolic-ref", Param "HEAD"] r
where
parse l
| null l = Nothing
| otherwise = Just $ Git.Ref l
{- Checks if the second branch has any commits not present on the first
- branch. -}
changed :: Branch -> Branch -> Repo -> IO Bool
changed origbranch newbranch repo
| origbranch == newbranch = return False
| otherwise = not . null <$> diffs
where
diffs = pipeReadStrict
[ Param "log"
, Param (show origbranch ++ ".." ++ show newbranch)
, Params "--oneline -n1"
] repo
{- Given a set of refs that are all known to have commits not
- on the branch, tries to update the branch by a fast-forward.
-
- In order for that to be possible, one of the refs must contain
- every commit present in all the other refs.
-}
fastForward :: Branch -> [Ref] -> Repo -> IO Bool
fastForward _ [] _ = return True
fastForward branch (first:rest) repo =
-- First, check that the branch does not contain any
-- new commits that are not in the first ref. If it does,
-- cannot fast-forward.
ifM (changed first branch repo)
( no_ff
, maybe no_ff do_ff =<< findbest first rest
)
where
no_ff = return False
do_ff to = do
run [Param "update-ref", Param $ show branch, Param $ show to] repo
return True
findbest c [] = return $ Just c
findbest c (r:rs)
| c == r = findbest c rs
| otherwise = do
better <- changed c r repo
worse <- changed r c repo
case (better, worse) of
(True, True) -> return Nothing -- divergent fail
(True, False) -> findbest r rs -- better
(False, True) -> findbest c rs -- worse
(False, False) -> findbest c rs -- same
{- Commits the index into the specified branch (or other ref),
- with the specified parent refs, and returns the committed sha -}
commit :: String -> Branch -> [Ref] -> Repo -> IO Sha
commit message branch parentrefs repo = do
tree <- getSha "write-tree" $
pipeReadStrict [Param "write-tree"] repo
sha <- getSha "commit-tree" $ pipeWriteRead
(map Param $ ["commit-tree", show tree] ++ ps)
message repo
run [Param "update-ref", Param $ show branch, Param $ show sha] repo
return sha
where
ps = concatMap (\r -> ["-p", show r]) parentrefs
|
