annex.fastcopy

Added annex.fastcopy and remote.name.annex-fastcopy config setting. When
set, this allows the copy_file_range syscall to be used, which can eg allow
for server-side copies on NFS. (For fastest copying, also disable
annex.verify or remote.name.annex-verify.)

This is a simple implementation, that does not handle resuming as well as
it possibly could.

It can be used with both local git remotes (including on NFS), and
directory special remotes. Other types of remotes could in theory also
support it, so I've left the config documented as a general thing.

Types/GitConfig.hs

@@ -1,6 +1,6 @@
 {- git-annex configuration
  -
- - Copyright 2012-2024 Joey Hess <id@joeyh.name>
+ - Copyright 2012-2025 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -135,6 +135,7 @@ data GitConfig = GitConfig
 	, annexDifferences :: Differences
 	, annexUsedRefSpec :: Maybe RefSpec
 	, annexVerify :: Bool
+	, annexFastCopy :: Bool
 	, annexPidLock :: Bool
 	, annexPidLockTimeout :: Seconds
 	, annexDbDir :: Maybe OsPath
@@ -241,6 +242,7 @@ extractGitConfig configsource r = GitConfig
 	, annexUsedRefSpec = either (const Nothing) Just . parseRefSpec 
 		=<< getmaybe (annexConfig "used-refspec")
 	, annexVerify = getbool (annexConfig "verify") True
+	, annexFastCopy = getbool (annexConfig "fastcopy") False
 	, annexPidLock = getbool (annexConfig "pidlock") False
 	, annexPidLockTimeout = Seconds $ fromMaybe 300 $
 		getmayberead (annexConfig "pidlocktimeout")
@@ -387,6 +389,7 @@ data RemoteGitConfig = RemoteGitConfig
 	, remoteAnnexPush :: Bool
 	, remoteAnnexReadOnly :: Bool
 	, remoteAnnexVerify :: Bool
+	, remoteAnnexFastCopy :: Bool
 	, remoteAnnexCheckUUID :: Bool
 	, remoteAnnexTrackingBranch :: Maybe Git.Ref
 	, remoteAnnexTrustLevel :: Maybe String
@@ -466,6 +469,7 @@ extractRemoteGitConfig r remotename = do
 		, remoteAnnexReadOnly = getbool ReadOnlyField False
 		, remoteAnnexCheckUUID = getbool CheckUUIDField True
 		, remoteAnnexVerify = getbool VerifyField True
+		, remoteAnnexFastCopy = getbool FastCopyField False
 		, remoteAnnexTrackingBranch = Git.Ref . encodeBS <$>
 			( notempty (getmaybe TrackingBranchField)
 			<|> notempty (getmaybe ExportTrackingField) -- old name
@@ -574,6 +578,7 @@ data RemoteGitConfigField
 	| ReadOnlyField
 	| CheckUUIDField
 	| VerifyField
+	| FastCopyField
 	| TrackingBranchField
 	| ExportTrackingField
 	| TrustLevelField
@@ -644,6 +649,7 @@ remoteGitConfigField = \case
 	ReadOnlyField -> inherited True "readonly"
 	CheckUUIDField -> uninherited True "checkuuid"
 	VerifyField -> inherited True "verify"
+	FastCopyField -> inherited True "fastcopy"
 	TrackingBranchField -> uninherited True "tracking-branch"
 	ExportTrackingField -> uninherited True "export-tracking"
 	TrustLevelField -> uninherited True "trustlevel"