add SeekInput (not yet used)

No behavior changes (hopefully), just adding SeekInput and plumbing it
through to the JSON display code for later use.

Over the course of 2 grueling days.

withFilesNotInGit reimplemented in terms of seekHelper
should be the only possible behavior change. It seems to test as
behaving the same.

Note that seekHelper dummies up the SeekInput in the case where
segmentPaths' gives up on sorting the expanded paths because there are
too many input paths. When SeekInput later gets exposed as a json field,
that will result in it being a little bit wrong in the case where
100 or more paths are passed to a git-annex command. I think this is a
subtle enough problem to not matter. If it does turn out to be a
problem, fixing it would require splitting up the input
parameters into groups of < 100, which would make git ls-files run
perhaps more than is necessary. May want to revisit this, because that
fix seems fairly low-impact.

Types/Command.hs

@@ -38,13 +38,18 @@ type CommandPerform = Annex (Maybe CommandCleanup)
  -    returns the overall success/fail of the command. -}
 type CommandCleanup = Annex Bool
 
+{- Input that was seeked on to make an ActionItem. Eg, the input filename,
+ - or directory name. -}
+newtype SeekInput = SeekInput [String]
+	deriving (Show)
+
 {- Message that is displayed when starting to perform an action on
  - something. The String is typically the name of the command or action
  - being performed.
  -}
 data StartMessage
-	= StartMessage String ActionItem
-	| StartUsualMessages String ActionItem
+	= StartMessage String ActionItem SeekInput
+	| StartUsualMessages String ActionItem SeekInput
 	-- ^ Like StartMessage, but makes sure to enable usual message
 	-- display in case it was disabled by cmdnomessages.
 	| StartNoMessage ActionItem
@@ -56,8 +61,8 @@ data StartMessage
 	deriving (Show)
 
 instance MkActionItem StartMessage where
-	mkActionItem (StartMessage _ ai) = ai
-	mkActionItem (StartUsualMessages _ ai) = ai
+	mkActionItem (StartMessage _ ai _) = ai
+	mkActionItem (StartUsualMessages _ ai _) = ai
 	mkActionItem (StartNoMessage ai) = ai
 	mkActionItem (CustomOutput ai) = ai