removal of the rest of remoteGitConfig

In keyUrls, the GitConfig is used only by annexLocations
to support configured Differences. Since such configurations affect all
clones of a repository, the local repo's GitConfig must have the same
information as the remote's GitConfig would have. So, used getGitConfig
to get the local GitConfig, which is cached and so available cheaply.

That actually fixed a bug noone had ever noticed: keyUrls is
used for remotes accessed over http. The full git config of such a
remote is normally not available, so the remoteGitConfig that keyUrls
used would not have the necessary information in it.

In copyFromRemoteCheap', it uses gitAnnexLocation,
which does need the GitConfig of the remote repo itself in order to
check if it's crippled, supports symlinks, etc. So, made the
State include that GitConfig, cached. The use of gitAnnexLocation is
within a (not $ Git.repoIsUrl repo) guard, so it's local, and so
its git config will always be read and available.

(Note that gitAnnexLocation in turn calls annexLocations, so the
Differences config it uses in this case comes from the remote repo's
GitConfig and not from the local repo's GitConfig. As explained above
this is ok since they must have the same value.)

Not very happy with this mess of different GitConfigs not type-safe and
some read only sometimes etc. Very hairy. Think I got it this change
right. Test suite passes..

This commit was sponsored by Ethan Aubin.

Types/GitConfig.hs

@@ -19,6 +19,7 @@ import Common
 import qualified Git
 import qualified Git.Config
 import qualified Git.Construct
+import Git.Types
 import Git.ConfigTypes
 import Utility.DataUnits
 import Config.Cost
@@ -195,7 +196,12 @@ mergeGitConfig gitconfig repoglobals = gitconfig
 
 {- Per-remote git-annex settings. Each setting corresponds to a git-config
  - key such as <remote>.annex-foo, or if that is not set, a default from
- - annex.foo -}
+ - annex.foo.
+ -
+ - Note that this is from the perspective of the local repository,
+ - it is not influenced in any way by the contents of the remote
+ - repository's git config.
+ -}
 data RemoteGitConfig = RemoteGitConfig
 	{ remoteAnnexCost :: DynamicConfig (Maybe Cost)
 	, remoteAnnexIgnore :: DynamicConfig Bool
@@ -235,11 +241,11 @@ data RemoteGitConfig = RemoteGitConfig
 	, remoteAnnexDdarRepo :: Maybe String
 	, remoteAnnexHookType :: Maybe String
 	, remoteAnnexExternalType :: Maybe String
-	{- A regular git remote's git repository config. -}
-	, remoteGitConfig :: GitConfig
 	}
 
-extractRemoteGitConfig :: Git.Repo -> String -> STM RemoteGitConfig
+{- The Git.Repo is the local repository, which has the remote with the
+ - given RemoteName. -}
+extractRemoteGitConfig :: Git.Repo -> RemoteName -> STM RemoteGitConfig
 extractRemoteGitConfig r remotename = do
 	annexcost <- mkDynamicConfig readCommandRunner
 		(notempty $ getmaybe "cost-command")
@@ -288,7 +294,6 @@ extractRemoteGitConfig r remotename = do
 		, remoteAnnexDdarRepo = getmaybe "ddarrepo"
 		, remoteAnnexHookType = notempty $ getmaybe "hooktype"
 		, remoteAnnexExternalType = notempty $ getmaybe "externaltype"
-		, remoteGitConfig = extractGitConfig r
 		}
   where
 	getbool k d = fromMaybe d $ getmaybebool k