lib: save the current date in ReportOpts

We need this for choosing a valuation date, otherwise, report
functions would have to be in IO or we'd have to pass in yet another
argument.

It's optional because it's useful to be able to create report opts
purely (I think ?) This is not ideal but maybe not a problem.

hledger-lib/Hledger/Reports/ReportOptions.hs

@@ -77,12 +77,15 @@ instance Default AccountListMode where def = ALDefault
 -- or query arguments, but not all. Some are used only by certain
 -- commands, as noted below. 
 data ReportOpts = ReportOpts {
-     period_         :: Period
+     today_          :: Maybe Day  -- ^ The current date. A late addition to ReportOpts.
+                                   -- Optional, but when set it may affect some reports:
+                                   -- Reports use it when picking a -V valuation date.
+    ,period_         :: Period
     ,interval_       :: Interval
     ,statuses_       :: [Status]  -- ^ Zero, one, or two statuses to be matched
     ,cost_           :: Bool
     ,depth_          :: Maybe Int
-    ,display_        :: Maybe DisplayExp
+    ,display_        :: Maybe DisplayExp  -- XXX unused ?
     ,date2_          :: Bool
     ,empty_          :: Bool
     ,no_elide_       :: Bool
@@ -146,6 +149,7 @@ defreportopts = ReportOpts
     def
     def
     def
+    def
 
 rawOptsToReportOpts :: RawOpts -> IO ReportOpts
 rawOptsToReportOpts rawopts = checkReportOpts <$> do
@@ -153,7 +157,8 @@ rawOptsToReportOpts rawopts = checkReportOpts <$> do
   d <- getCurrentDay
   color <- hSupportsANSI stdout
   return defreportopts{
-     period_      = periodFromRawOpts d rawopts'
+     today_       = Just d
+    ,period_      = periodFromRawOpts d rawopts'
     ,interval_    = intervalFromRawOpts rawopts'
     ,statuses_    = statusesFromRawOpts rawopts'
     ,cost_        = boolopt "cost" rawopts'