Clean up handling of git directory and git worktree.

Baked into the code was an assumption that a repository's git directory
could be determined by adding ".git" to its work tree (or nothing for bare
repos). That fails when core.worktree, or GIT_DIR and GIT_WORK_TREE are
used to separate the two.

This was attacked at the type level, by storing the gitdir and worktree
separately, so Nothing for the worktree means a bare repo.

A complication arose because we don't learn where a repository is bare
until its configuration is read. So another Location type handles
repositories that have not had their config read yet. I am not entirely
happy with this being a Location type, rather than representing them
entirely separate from the Git type. The new code is not worse than the
old, but better types could enforce more safety.

Added support for core.worktree. Overriding it with -c isn't supported
because it's not really clear what to do if a git repo's config is read, is
not bare, and is then overridden to bare. What is the right git directory
in this case? I will worry about this if/when someone has a use case for
overriding core.worktree with -c. (See Git.Config.updateLocation)

Also removed and renamed some functions like gitDir and workTree that
misused git's terminology.

One minor regression is known: git annex add in a bare repository does not
print a nice error message, but runs git ls-files in a way that fails
earlier with a less nice error message. This is because before --work-tree
was always passed to git commands, even in a bare repo, while now it's not.

1 files changed, 16 insertions, 4 deletions

diff --git a/Git/Types.hs b/Git/Types.hs
index 6063ad213..deb14ebd4 100644
--- a/Git/Types.hs
+++ b/Git/Types.hs
@@ -1,6 +1,6 @@
 {- git data types
  -
- - Copyright 2010,2011 Joey Hess <joey@kitenet.net>
+ - Copyright 2010-2012 Joey Hess <joey@kitenet.net>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -10,9 +10,21 @@ module Git.Types where
 import Network.URI
 import qualified Data.Map as M
 
-{- There are two types of repositories; those on local disk and those
- - accessed via an URL. -}
-data RepoLocation = Dir FilePath | Url URI | Unknown
+{- Support repositories on local disk, and repositories accessed via an URL.
+ -
+ - Repos on local disk have a git directory, and unless bare, a worktree.
+ -
+ - A local repo may not have had its config read yet, in which case all
+ - that's known about it is its path.
+ -
+ - Finally, an Unknown repository may be known to exist, but nothing
+ - else known about it.
+ -}
+data RepoLocation
+	= Local { gitdir :: FilePath, worktree :: Maybe FilePath }
+	| LocalUnknown FilePath
+	| Url URI
+	| Unknown
 	deriving (Show, Eq)
 
 data Repo = Repo {