add git annex view command

(And a vpop command, which is still a bit buggy.)

Still need to do vadd and vrm, though this also adds their documentation.

Currently not very happy with the view log data serialization. I had to
lose the TDFA regexps temporarily, so I can have Read/Show instances of
View. I expect the view log format will change in some incompatable way
later, probably adding last known refs for the parent branch to View
or something like that.

Anyway, it basically works, although it's a bit slow looking up the
metadata. The actual git branch construction is about as fast as it can be
using the current git plumbing.

This commit was sponsored by Peter Hogg.

1 files changed, 3 insertions, 3 deletions

diff --git a/Types/MetaData.hs b/Types/MetaData.hs
index 248a96abb..601757315 100644
--- a/Types/MetaData.hs
+++ b/Types/MetaData.hs
@@ -53,13 +53,13 @@ newtype MetaData = MetaData (M.Map MetaField (S.Set MetaValue))
 {- A metadata value can be currently be set (True), or may have been
  - set before and we're remembering it no longer is (False). -}
 newtype CurrentlySet = CurrentlySet Bool
-	deriving (Show, Eq, Ord, Arbitrary)
+	deriving (Read, Show, Eq, Ord, Arbitrary)
 
 newtype MetaField = MetaField String
-	deriving (Show, Eq, Ord)
+	deriving (Read, Show, Eq, Ord)
 
 data MetaValue = MetaValue CurrentlySet String
-	deriving (Show)
+	deriving (Read, Show)
 
 {- Metadata values compare and order the same whether currently set or not. -}
 instance Eq MetaValue where