git-annex/Command/Mirror.hs
Joey Hess 34c8af74ba fix inversion of control in CommandSeek (no behavior changes)
I've been disliking how the command seek actions were written for some
time, with their inversion of control and ugly workarounds.

The last straw to fix it was sync --content, which didn't fit the
Annex [CommandStart] interface well at all. I have not yet made it take
advantage of the changed interface though.

The crucial change, and probably why I didn't do it this way from the
beginning, is to make each CommandStart action be run with exceptions
caught, and if it fails, increment a failure counter in annex state.
So I finally remove the very first code I wrote for git-annex, which
was before I had exception handling in the Annex monad, and so ran outside
that monad, passing state explicitly as it ran each CommandStart action.

This was a real slog from 1 to 5 am.

Test suite passes.

Memory usage is lower than before, sometimes by a couple of megabytes, and
remains constant, even when running in a large repo, and even when
repeatedly failing and incrementing the error counter. So no accidental
laziness space leaks.

Wall clock speed is identical, even in large repos.

This commit was sponsored by an anonymous bitcoiner.
2014-01-20 04:57:36 -04:00

62 lines
1.8 KiB
Haskell

{- git-annex command
-
- Copyright 2013 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Command.Mirror where
import Common.Annex
import Command
import GitAnnex.Options
import qualified Command.Move
import qualified Command.Drop
import qualified Command.Get
import qualified Remote
import Annex.Content
import qualified Annex
def :: [Command]
def = [withOptions (fromToOptions ++ keyOptions) $
command "mirror" paramPaths seek
SectionCommon "mirror content of files to/from another repository"]
seek :: CommandSeek
seek ps = do
to <- getOptionField toOption Remote.byNameWithUUID
from <- getOptionField fromOption Remote.byNameWithUUID
withKeyOptions
(startKey Nothing to from Nothing)
(withFilesInGit $ whenAnnexed $ start to from)
ps
start :: Maybe Remote -> Maybe Remote -> FilePath -> (Key, Backend) -> CommandStart
start to from file (key, _backend) = do
numcopies <- numCopies file
startKey numcopies to from (Just file) key
startKey :: Maybe Int -> Maybe Remote -> Maybe Remote -> Maybe FilePath -> Key -> CommandStart
startKey numcopies to from afile key = do
noAuto
case (from, to) of
(Nothing, Nothing) -> error "specify either --from or --to"
(Nothing, Just r) -> mirrorto r
(Just r, Nothing) -> mirrorfrom r
_ -> error "only one of --from or --to can be specified"
where
noAuto = whenM (Annex.getState Annex.auto) $
error "--auto is not supported for mirror"
mirrorto r = ifM (inAnnex key)
( Command.Move.toStart r False afile key
, Command.Drop.startRemote afile numcopies key r
)
mirrorfrom r = do
haskey <- Remote.hasKey r key
case haskey of
Left _ -> stop
Right True -> Command.Get.start' (return True) Nothing key afile
Right False -> ifM (inAnnex key)
( Command.Drop.startLocal afile numcopies key Nothing
, stop
)