--anything and --nothing

Added --anything (and --nothing). Eg, git-annex find --anything will list
all annexed files whether or not the content is present. This is slightly
faster and clearer than --include=* or --exclude=*

While I can't imagine how --nothing will be used, preferred content
expressions already had anything and nothing, so might as well support both
as matching options as well.

Sponsored-by: Dartmouth College's Datalad project

CmdLine/GitAnnex/Options.hs

@@ -378,6 +378,16 @@ fileMatchingOptions' lb =
 		<> help "match files smaller than a size"
 		<> hidden
 		)
+	, annexFlag (setAnnexState Limit.addAnything)
+		( long "anything"
+		<> help "match all files"
+		<> hidden
+		)
+	, annexFlag (setAnnexState Limit.addNothing)
+		( long "nothing"
+		<> help "don't match any files"
+		<> hidden
+		)
 	]
 
 combiningOptions :: [AnnexOption]