adda6c1088
Significant startup speed increase by avoiding repeatedly checking if some remote git-annex branch refs need to be merged when it is not newer. One way this could happen is when there are 2 remotes that are themselves connected. The git-annex branch on the first remote gets updated. Then the second remote pulls from the first, and merges in its git-annex branch. Then the local repo pulls from the second remote, and merges its git-annex branch. At this point, a pull from the first remote will get a git-annex branch that is not newer, but is not on the merged refs list. In my big repo, git-annex startup time dropped from 4 seconds to 0.1 seconds. There were 5 to 10 such remote refs out of 18 remotes. Sponsored-by: Graham Spencer on Patreon
91 lines
2.2 KiB
Haskell
91 lines
2.2 KiB
Haskell
{- monadic stuff
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-
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- Copyright 2010-2012 Joey Hess <id@joeyh.name>
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-
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- License: BSD-2-clause
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-}
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{-# OPTIONS_GHC -fno-warn-tabs #-}
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module Utility.Monad (
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firstM,
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getM,
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anyM,
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allM,
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partitionM,
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untilTrue,
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ifM,
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(<||>),
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(<&&>),
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observe,
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after,
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noop,
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) where
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import Data.Maybe
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import Control.Monad
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{- Return the first value from a list, if any, satisfying the given
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- predicate -}
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firstM :: Monad m => (a -> m Bool) -> [a] -> m (Maybe a)
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firstM _ [] = return Nothing
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firstM p (x:xs) = ifM (p x) (return $ Just x , firstM p xs)
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{- Runs the action on values from the list until it succeeds, returning
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- its result. -}
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getM :: Monad m => (a -> m (Maybe b)) -> [a] -> m (Maybe b)
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getM _ [] = return Nothing
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getM p (x:xs) = maybe (getM p xs) (return . Just) =<< p x
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{- Returns true if any value in the list satisfies the predicate,
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- stopping once one is found. -}
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anyM :: Monad m => (a -> m Bool) -> [a] -> m Bool
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anyM p = liftM isJust . firstM p
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allM :: Monad m => (a -> m Bool) -> [a] -> m Bool
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allM _ [] = return True
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allM p (x:xs) = p x <&&> allM p xs
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partitionM :: Monad m => (a -> m Bool) -> [a] -> m ([a], [a])
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partitionM _ [] = return ([], [])
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partitionM p (x:xs) = do
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r <- p x
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(as, bs) <- partitionM p xs
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return $ if r then (x:as, bs) else (as, x:bs)
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{- Runs an action on values from a list until it succeeds. -}
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untilTrue :: Monad m => [a] -> (a -> m Bool) -> m Bool
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untilTrue = flip anyM
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{- if with a monadic conditional. -}
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ifM :: Monad m => m Bool -> (m a, m a) -> m a
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ifM cond (thenclause, elseclause) = do
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c <- cond
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if c then thenclause else elseclause
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{- short-circuiting monadic || -}
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(<||>) :: Monad m => m Bool -> m Bool -> m Bool
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ma <||> mb = ifM ma ( return True , mb )
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{- short-circuiting monadic && -}
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(<&&>) :: Monad m => m Bool -> m Bool -> m Bool
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ma <&&> mb = ifM ma ( mb , return False )
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{- Same fixity as && and || -}
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infixr 3 <&&>
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infixr 2 <||>
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{- Runs an action, passing its value to an observer before returning it. -}
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observe :: Monad m => (a -> m b) -> m a -> m a
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observe observer a = do
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r <- a
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_ <- observer r
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return r
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{- b `after` a runs first a, then b, and returns the value of a -}
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after :: Monad m => m b -> m a -> m a
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after = observe . const
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{- do nothing -}
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noop :: Monad m => m ()
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noop = return ()
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