initremote type=git probe uuid

rather than matching path of an existing remote to find the uuid.

The main benefit of this is that locations not using ssh:// will work
now, including both paths and host:/path

The other benefit is that it's a simpler interface, no need to have an
existing remote with the same url and some other name. Although that
will still work of course.

This does rely on tryGitConfigRead working when given a Git.Repo that is
not a remote. Luckily, it works fine that way.

Also, tryGitConfigRead will auto-init a local repo that has a git-annex
branch. I did not enable auto-init of ssh repos though.

The uuid discovery actually happens twice; initremote discovers it,
and uses it to store the special remote config, but does not set it in the
git remote it creates. So the next run of git-annex does uuid discovery
again, and caches it that time. This could be improved for a tiny
speedup, but I didn't want to complicate things for that in this
commit.

Sponsored-by: Dartmouth College's DANDI project

Remote/Git.hs

@@ -107,11 +107,11 @@ list autoinit = do
 				Git.Construct.remoteNamed n $
 					Git.Construct.fromRemoteLocation (Git.fromConfigValue url) g
 
-{- Git remotes are normally set up using standard git command, not
+{- Git remotes are normally set up using standard git commands, not
  - git-annex initremote and enableremote.
  -
- - For initremote, the git remote must already be set up, and have a uuid.
- - Initremote simply remembers its location.
+ - For initremote, probe the location to find the uuid.
+ - and set up a git remote.
  -
  - enableremote simply sets up a git remote using the stored location.
  - No attempt is made to make the remote be accessible via ssh key setup,
@@ -119,17 +119,16 @@ list autoinit = do
  -}
 gitSetup :: SetupStage -> Maybe UUID -> Maybe CredPair -> RemoteConfig -> RemoteGitConfig -> Annex (RemoteConfig, UUID)
 gitSetup Init mu _ c _ = do
-	let location = fromMaybe (giveup "Specify location=url") $
-		Url.parseURIRelaxed . fromProposedAccepted
-			=<< M.lookup locationField c
-	rs <- Annex.getGitRemotes
-	u <- case filter (\r -> Git.location r == Git.Url location) rs of
-		[r] -> getRepoUUID r
-		[] -> giveup "could not find existing git remote with specified location"
-		_ -> giveup "found multiple git remotes with specified location"
-	if isNothing mu || mu == Just u
-		then return (c, u)
-		else error "git remote did not have specified uuid"
+	let location = maybe (giveup "Specify location=url") fromProposedAccepted $
+		M.lookup locationField c
+	r <- inRepo $ Git.Construct.fromRemoteLocation location
+	r' <- tryGitConfigRead False r False
+	let u = getUncachedUUID r'
+	if u == NoUUID
+		then gitveup "git repository does not have an annex uuid"
+		else if isNothing mu || mu == Just u
+			then enableRemote (Just u) c
+			else giveup "git repository does not have specified uuid"
 gitSetup (Enable _) mu _ c _ = enableRemote mu c
 gitSetup (AutoEnable _) mu _ c _ = enableRemote mu c
 
@@ -142,7 +141,7 @@ enableRemote (Just u) c = do
 		, Param $ maybe (giveup "no location") fromProposedAccepted (M.lookup locationField c)
 		]
 	return (c, u)
-enableRemote Nothing _ = error "unable to enable git remote with no specified uuid"
+enableRemote Nothing _ = giveup "unable to enable git remote with no specified uuid"
 
 {- It's assumed to be cheap to read the config of non-URL remotes, so this is
  - done each time git-annex is run in a way that uses remotes, unless