add --sameas option, not yet used

CHANGELOG

@@ -14,6 +14,8 @@ git-annex (7.20190913) UNRELEASED; urgency=medium
   * Fix bug in handling of annex.largefiles that use largerthan/smallerthan.
     When adding a modified file, it incorrectly used the file size of the
     old version of the file, not the current size.
+  * initremote: Added --sameas option, allows for two special remotes that
+    access the same data store.
 
  -- Joey Hess <id@joeyh.name>  Thu, 19 Sep 2019 11:11:19 -0400
 

CmdLine/GitAnnex/Options.hs

@@ -1,6 +1,6 @@
 {- git-annex command-line option parsing
  -
- - Copyright 2010-2018 Joey Hess <id@joeyh.name>
+ - Copyright 2010-2019 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -114,6 +114,10 @@ parseRemoteOption = DeferredParse
 	. (fromJust <$$> Remote.byNameWithUUID)
 	. Just
 
+parseUUIDOption :: String -> DeferredParse UUID
+parseUUIDOption = DeferredParse
+	. (Remote.nameToUUID)
+
 -- | From or To a remote.
 data FromToOptions
 	= FromRemote (DeferredParse Remote)

Command/InitRemote.hs

@@ -1,6 +1,6 @@
 {- git-annex command
  -
- - Copyright 2011,2013 Joey Hess <id@joeyh.name>
+ - Copyright 2011-2019 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -21,14 +21,32 @@ cmd :: Command
 cmd = command "initremote" SectionSetup
 	"creates a special (non-git) remote"
 	(paramPair paramName $ paramOptional $ paramRepeating paramKeyValue)
-	(withParams seek)
+	(seek <$$> optParser)
 
-seek :: CmdParams -> CommandSeek
-seek = withWords (commandAction . start)
+data InitRemoteOptions = InitRemoteOptions
+	{ cmdparams :: CmdParams
+	, sameas :: Maybe (DeferredParse UUID)
+	}
 
-start :: [String] -> CommandStart
-start [] = giveup "Specify a name for the remote."
-start (name:ws) = ifM (isJust <$> findExisting name)
+optParser :: CmdParamsDesc -> Parser InitRemoteOptions
+optParser desc = InitRemoteOptions
+	<$> cmdParams desc
+	<*> optional parseSameasOption
+
+parseSameasOption :: Parser (DeferredParse UUID)
+parseSameasOption = parseUUIDOption <$> strOption
+	( long "sameas"
+	<> metavar (paramRemote `paramOr` paramDesc `paramOr` paramUUID)
+	<> help "new remote that accesses the same data"
+	<> completeRemotes
+	)
+
+seek :: InitRemoteOptions -> CommandSeek
+seek o = withWords (commandAction . (start o)) (cmdparams o)
+
+start :: InitRemoteOptions -> [String] -> CommandStart
+start _ [] = giveup "Specify a name for the remote."
+start o (name:ws) = ifM (isJust <$> findExisting name)
 	( giveup $ "There is already a special remote named \"" ++ name ++
 		"\". (Use enableremote to enable an existing special remote.)"
 	, do

doc/git-annex-initremote.mdwn

@@ -43,6 +43,20 @@ want to use `git annex renameremote`.
   and re-run with `--fast`, which causes it to use a lower-quality source of
   randomness. (Ie, /dev/urandom instead of /dev/random)
 
+* `--sameas=remote`
+
+  Use this when the new special remote uses the same underlying storage
+  as some other remote. This will result in the new special remote having
+  the same uuid as the specified remote, and either can be used to access
+  the same content.
+
+  The `remote` can be the name of a git remote, or the description
+  or uuid of any git-annex repository.
+
+  When using this option, the new remote inherits the encryption settings
+  of the existing remote, so you should not specify any encryption
+  parameters. No other configuration is inherited from the existing remote.
+
 # COMMON CONFIGURATION PARAMETERS
 
 * `encryption`

doc/todo/git-lfs_special_remote_simpler_setup.mdwn

@@ -14,6 +14,11 @@ two. url=http:// url=ssh:// won't work, only one value will be used.
 url1= url2= is annoying for the user, especially if they later want to add
 another url with enableremote and have to work out the number.
 
+> If each url is treated as a separate special remote (which makes a lot of sense
+> by analogy with how regular git remotes work), then
+> [[support_multiple_special_remotes_with_same_uuid]] could be used to
+> solve this.
+
 Problem: The user might go in and change the remote's url to point to some
 other server with a different git-lfs backend. In fact, they could already
 do so! Remembering the urls actually would let the special remote detect

doc/todo/support_multiple_special_remotes_with_same_uuid/comment_4_76d747fe5fb8296d8728cc3af7503972._comment

@@ -0,0 +1,14 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 4"""
+ date="2019-10-01T16:26:12Z"
+ content="""
+The RemoteConfig is generated each run from the remote.log, and so the
+handling of sameas remotes needs to be done in Logs.Remote.readRemoteLog
+not by enableremote.
+
+Logs.Remote.configSet will need some changes because it currently works
+on the basis of UUID, and so can't know when it's supposed to change a
+sameas remote. It seems it should instead work on the basis of the "name"
+field of the RemoteConfig.
+"""]]