annexInsteadOf config

Added config `url.<base>.annexInsteadOf` corresponding to git's
`url.<base>.pushInsteadOf`, to configure the urls to use for accessing the
git-annex repositories on a server without needing to configure
remote.name.annexUrl in each repository.

While one use case for this would be rewriting urls to use annex+http,
I decided not to add any kind of special case for that. So while
git-annex p2phttp, when serving multiple repositories, needs an url
of eg "annex+http://example.com/git-annex/ for each of them, rewriting an
url like "https://example.com/git/foo/bar" with this config set to
"https://example.com/git/" will result in eg
"annex+http://example.com/git-annex/foo/bar", which p2phttp does not
support.

That seems better dealt with in either git-annex p2phttp or a http
middleware, rather than complicating the config with a special case for
annex+http.

Anyway, there are other use cases for this that don't involve annex+http.

Git/Types.hs

@@ -41,9 +41,9 @@ data RepoLocation
 
 data Repo = Repo
 	{ location :: RepoLocation
-	, config :: M.Map ConfigKey ConfigValue
+	, config :: RepoConfig
 	-- a given git config key can actually have multiple values
-	, fullconfig :: M.Map ConfigKey (NE.NonEmpty ConfigValue)
+	, fullconfig :: RepoFullConfig
 	-- remoteName holds the name used for this repo in some other
 	-- repo's list of remotes, when this repo is such a remote
 	, remoteName :: Maybe RemoteName
@@ -60,6 +60,10 @@ data Repo = Repo
 	-- when using this repository.
 	, repoPathSpecifiedExplicitly :: Bool
 	} deriving (Show, Eq, Ord)
+	
+type RepoConfig = M.Map ConfigKey ConfigValue
+
+type RepoFullConfig = M.Map ConfigKey (NE.NonEmpty ConfigValue)
 
 newtype ConfigKey = ConfigKey S.ByteString
 	deriving (Ord, Eq)