start borg special remote

Compiles, but unusable so far.

Remote/Borg.hs

@@ -0,0 +1,105 @@
+{- Using borg as a remote.
+ -
+ - Copyright 2020 Joey Hess <id@joeyh.name>
+ -
+ - Licensed under the GNU AGPL version 3 or higher.
+ -}
+
+module Remote.Borg (remote) where
+
+import Annex.Common
+import Types.Remote
+import Types.Creds
+import qualified Git
+import Config
+import Config.Cost
+import Annex.SpecialRemote.Config
+import Remote.Helper.Special
+import Remote.Helper.ExportImport
+import Annex.UUID
+import Types.ProposedAccepted
+
+import qualified Data.Map as M
+
+type BorgRepo = String
+
+remote :: RemoteType
+remote = RemoteType
+	{ typename = "borg"
+	, enumerate = const (findSpecialRemotes "borgrepo")
+	, generate = gen
+	, configParser = mkRemoteConfigParser
+		[ optionalStringParser borgrepoField
+			(FieldDesc "(required) borg repository to use")
+		]
+	, setup = borgSetup
+	, exportSupported = exportUnsupported
+	, importSupported = importIsSupported
+	, thirdPartyPopulated = True
+	}
+
+borgrepoField :: RemoteConfigField
+borgrepoField = Accepted "borgrepo"
+
+gen :: Git.Repo -> UUID -> RemoteConfig -> RemoteGitConfig -> RemoteStateHandle -> Annex (Maybe Remote)
+gen r u rc gc rs = do
+	c <- parsedRemoteConfig remote rc
+	cst <- remoteCost gc $
+		if borgLocal borgrepo
+			then nearlyCheapRemoteCost
+			else expensiveRemoteCost
+	return $ Just $ Remote
+		{ uuid = u
+		, cost = cst
+		, name = Git.repoDescribe r
+		, storeKey = storeKeyDummy
+		, retrieveKeyFile = retrieveKeyFileDummy
+		, retrieveKeyFileCheap = Nothing
+		-- Borg cryptographically verifies content.
+		, retrievalSecurityPolicy = RetrievalAllKeysSecure
+		, removeKey = removeKeyDummy
+		, lockContent = Nothing
+		, checkPresent = checkPresentDummy
+		, checkPresentCheap = borgLocal borgrepo
+		, exportActions = exportUnsupported
+		, importActions = importUnsupported
+		, whereisKey = Nothing
+		, remoteFsck = Nothing
+		, repairRepo = Nothing
+		, config = c
+		, getRepo = return r
+		, gitconfig = gc
+		, localpath = if borgLocal borgrepo && not (null borgrepo)
+			then Just borgrepo
+			else Nothing
+		, remotetype = remote
+		, availability = if borgLocal borgrepo then LocallyAvailable else GloballyAvailable
+		, readonly = False
+		, appendonly = False
+		, mkUnavailable = return Nothing
+		, getInfo = return [("repo", borgrepo)]
+		, claimUrl = Nothing
+		, checkUrl = Nothing
+		, remoteStateHandle = rs
+		}
+  where
+	borgrepo = fromMaybe (giveup "missing borgrepo") $ remoteAnnexBorgRepo gc
+
+borgSetup :: SetupStage -> Maybe UUID -> Maybe CredPair -> RemoteConfig -> RemoteGitConfig -> Annex (RemoteConfig, UUID)
+borgSetup _ mu _ c _gc = do
+	u <- maybe (liftIO genUUID) return mu
+
+	-- verify configuration is sane
+	let borgrepo = maybe (giveup "Specify borgrepo=") fromProposedAccepted $
+		M.lookup borgrepoField c
+
+	-- The borgrepo is stored in git config, as well as this repo's
+	-- persistant state, so it can vary between hosts.
+	gitConfigSpecialRemote u c [("borgrepo", borgrepo)]
+
+	-- TODO: untrusted by default, but allow overriding that
+
+	return (c, u)
+
+borgLocal :: BorgRepo -> Bool
+borgLocal = notElem ':'

Remote/List.hs

@@ -36,6 +36,7 @@ import qualified Remote.Glacier
 import qualified Remote.Ddar
 import qualified Remote.GitLFS
 import qualified Remote.HttpAlso
+import qualified Remote.Borg
 import qualified Remote.Hook
 import qualified Remote.External
 
@@ -57,6 +58,7 @@ remoteTypes = map adjustExportImportRemoteType
 	, Remote.Ddar.remote
 	, Remote.GitLFS.remote
 	, Remote.HttpAlso.remote
+	, Remote.Borg.remote
 	, Remote.Hook.remote
 	, Remote.External.remote
 	]

Types/GitConfig.hs

@@ -327,6 +327,7 @@ data RemoteGitConfig = RemoteGitConfig
 	, remoteAnnexGnupgDecryptOptions :: [String]
 	, remoteAnnexRsyncUrl :: Maybe String
 	, remoteAnnexBupRepo :: Maybe String
+	, remoteAnnexBorgRepo :: Maybe String
 	, remoteAnnexTahoe :: Maybe FilePath
 	, remoteAnnexBupSplitOptions :: [String]
 	, remoteAnnexDirectory :: Maybe FilePath
@@ -391,6 +392,7 @@ extractRemoteGitConfig r remotename = do
 		, remoteAnnexGnupgDecryptOptions = getoptions "gnupg-decrypt-options"
 		, remoteAnnexRsyncUrl = notempty $ getmaybe "rsyncurl"
 		, remoteAnnexBupRepo = getmaybe "buprepo"
+		, remoteAnnexBorgRepo = getmaybe "borgrepo"
 		, remoteAnnexTahoe = getmaybe "tahoe"
 		, remoteAnnexBupSplitOptions = getoptions "bup-split-options"
 		, remoteAnnexDirectory = notempty $ getmaybe "directory"

doc/devblog/day_637__thirdparty_of_borg.mdwn

@@ -0,0 +1,17 @@
+Finally gotten started on the borg special remote idea. A prerequisite of
+that is remotes that can be imported from, but not exported to. So I
+actually started by allowing setting importtree=yes without
+exporttree=yes. A lot of code had assumptions about that not being allowed,
+so it took a while to chase down everything. Finished most of that yesterday.
+
+What I've done today is added a `thirdPartyPopulated` type of remote,
+which `git-annex sync` can "pull" from by using the existing import
+interface to list files on it, and determine which of them are annex object
+files. I have not started on the actual borg remote at all, but this should
+be all the groundwork for it done.
+
+(I also finished up annex.stalldetection earlier this week.)
+
+---
+
+This work was sponsored by Jake Vosloo [on Patreon](https://patreon.com/joeyh).

doc/git-annex.mdwn

@@ -1541,6 +1541,12 @@ Remotes are configured using these settings in `.git/config`.
   the location of the bup repository to use. Normally this is automatically
   set up by `git annex initremote`, but you can change it if needed.
 
+* `remote.<name>.annex-borgrepo`
+
+  Used by borg special remotes, this configures
+  the location of the borg repository to use. Normally this is automatically
+  set up by `git annex initremote`, but you can change it if needed.
+
 * `remote.<name>.annex-ddarrepo`
 
   Used by ddar special remotes, this configures

doc/special_remotes/borg.mdwn

@@ -11,7 +11,7 @@ the annexed files that are stored in the borg repository.
 These parameters can be passed to `git annex initremote` to configure the
 remote:
 
-* `repository` - The location of a borg repository, eg a path, or
+* `borgrepo` - The location of a borg repository, eg a path, or
   `user@host:path` for ssh access.
 
 * `scan` - The path, within the borg repository, to scan for
@@ -27,7 +27,7 @@ remote:
 ## setup example
 
 	# borg init --encryption=keyfile /path/to/borgrepo
-	# git annex initremote borg type=borg repository=/path/to/borgrepo scan=`pwd`
+	# git annex initremote borg type=borg borgrepo=/path/to/borgrepo scan=`pwd`
 	# borg create /path/to/borgrepo `pwd`::{now}
 	# git annex sync borg
 

git-annex.cabal

@@ -940,6 +940,7 @@ Executable git-annex
     Remote
     Remote.Adb
     Remote.BitTorrent
+    Remote.Borg
     Remote.Bup
     Remote.Ddar
     Remote.Directory