Submodules are now supported by git-annex!

Seems to work, but still experimental until it's been tested more.

When repositories are on filesystems not supporting symlinks, the .git dir
symlink trick cannot be used. Since we're going to be in direct mode
anyway, the .git dir symlink is not strictly needed.

However, I have not fixed the code that creates new annex symlinks to
handle this case -- the committed symlinks will be wrong.

git annex sync happens to currently fail in a submodule using direct mode,
because there's no HEAD ref. That also needs to be dealt with to get
this fully working in crippled filesystems.

Leaving http://github.com/datalad/datalad/issues/44 open until these issues
are dealt with.

Annex/Direct.hs

@@ -406,7 +406,25 @@ setDirect wantdirect = do
 	Annex.changeGitConfig $ \c -> c { annexDirect = wantdirect }
   where
 	val = Git.Config.boolConfig wantdirect
-	setbare = setConfig (ConfigKey Git.Config.coreBare) val
+	coreworktree = ConfigKey "core.worktree"
+	indirectworktree = ConfigKey "core.indirect-worktree"
+	setbare = do
+		-- core.worktree is not compatable with
+		-- core.bare; git does not allow both to be set, so
+		-- unset it when enabling direct mode, caching in
+		-- core.indirect-worktree
+		if wantdirect
+			then moveconfig coreworktree indirectworktree
+			else moveconfig indirectworktree coreworktree
+		setConfig (ConfigKey Git.Config.coreBare) val
+	moveconfig src dest = do
+		v <- getConfigMaybe src
+		case v of
+			Nothing -> noop
+			Just wt -> do
+				unsetConfig src
+				setConfig dest wt
+				reloadConfig
 
 {- Since direct mode sets core.bare=true, incoming pushes could change
  - the currently checked out branch. To avoid this problem, HEAD

Annex/Direct/Fixup.hs

@@ -1,31 +0,0 @@
-{- git-annex direct mode guard fixup
- -
- - Copyright 2013 Joey Hess <id@joeyh.name>
- -
- - Licensed under the GNU GPL version 3 or higher.
- -}
-
-module Annex.Direct.Fixup where
-
-import Git.Types
-import Git.Config
-import qualified Git.Construct as Construct
-import Utility.Path
-import Utility.SafeCommand
-
-{- Direct mode repos have core.bare=true, but are not really bare.
- - Fix up the Repo to be a non-bare repo, and arrange for git commands
- - run by git-annex to be passed parameters that override this setting. -}
-fixupDirect :: Repo -> IO Repo
-fixupDirect r@(Repo { location = l@(Local { gitdir = d, worktree = Nothing }) }) = do
-	let r' = r
-		{ location = l { worktree = Just (parentDir d) }
-		, gitGlobalOpts = gitGlobalOpts r ++
-			[ Param "-c"
-			, Param $ coreBare ++ "=" ++ boolConfig False
-			]
-		}
-	-- Recalc now that the worktree is correct.
-	rs' <- Construct.fromRemotes r'
-	return $ r' { remotes = rs' }
-fixupDirect r = return r

Annex/Fixup.hs

@@ -0,0 +1,86 @@
+{- git-annex repository fixups
+ -
+ - Copyright 2013, 2015 Joey Hess <id@joeyh.name>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Annex.Fixup where
+
+import Git.Types
+import Git.Config
+import Types.GitConfig
+import qualified Git.Construct as Construct
+import Utility.Path
+import Utility.SafeCommand
+import Utility.Directory
+import Utility.PosixFiles
+import Utility.Exception
+
+import System.IO
+import System.FilePath
+import System.Directory
+import Data.List
+import Control.Monad
+import Control.Monad.IfElse
+import qualified Data.Map as M
+
+fixupRepo :: Repo -> GitConfig -> IO Repo
+fixupRepo r c = do
+	r' <- fixupSubmodule r c
+	if annexDirect c
+		then fixupDirect r'
+		else return r'
+
+{- Direct mode repos have core.bare=true, but are not really bare.
+ - Fix up the Repo to be a non-bare repo, and arrange for git commands
+ - run by git-annex to be passed parameters that override this setting. -}
+fixupDirect :: Repo -> IO Repo
+fixupDirect r@(Repo { location = l@(Local { gitdir = d, worktree = Nothing }) }) = do
+	let r' = r
+		{ location = l { worktree = Just (parentDir d) }
+		, gitGlobalOpts = gitGlobalOpts r ++
+			[ Param "-c"
+			, Param $ coreBare ++ "=" ++ boolConfig False
+			]
+		}
+	-- Recalc now that the worktree is correct.
+	rs' <- Construct.fromRemotes r'
+	return $ r' { remotes = rs' }
+fixupDirect r = return r
+
+{- Submodules have their gitdir containing ".git/modules/", and
+ - have core.worktree set, and also have a .git file in the top
+ - of the repo. 
+ -
+ - We need to unset core.worktree, and change the .git file into a
+ - symlink to the git directory. This way, annex symlinks will be
+ - of the usual .git/annex/object form, and will consistently work
+ - whether a repo is used as a submodule or not, and wheverever the
+ - submodule is mounted.
+ -
+ - When the filesystem doesn't support symlinks, we cannot make .git
+ - into a symlink. In this case, we merely adjust the Repo so that
+ - symlinks to objects that get checked in will be in the right form.
+ -}
+fixupSubmodule :: Repo -> GitConfig -> IO Repo
+fixupSubmodule r@(Repo { location = l@(Local { worktree = Just w, gitdir = d }) }) c
+	| (".git" </> "modules") `isInfixOf` d = do
+		when (coreSymlinks c) $
+			replacedotgit
+				`catchNonAsync` \_e -> hPutStrLn stderr
+					"warning: unable to convert submodule to form that will work with git-annex"
+		return $ r
+			{ location = if coreSymlinks c
+				then l { gitdir = dotgit }
+				else l
+			, config = M.delete "core.worktree" (config r)
+			}
+  where
+	dotgit = w </> ".git"
+	replacedotgit = whenM (doesFileExist dotgit) $ do
+		nukeFile dotgit
+		createSymbolicLink (w </> d) dotgit
+		maybe (error "unset core.worktree failed") (\_ -> return ())
+			=<< Git.Config.unset "core.worktree" r
+fixupSubmodule r _ = return r