balance: with --flat, --drop N elides leading account name components. Feature or frill ?

Hledger/Cli/Commands/Balance.hs

@@ -140,7 +140,7 @@ showInterestingAccount opts l interestingaccts a = concatTopPadded [amt, "  ", n
       bal | Flat `elem` opts = exclusiveBalance acct
           | otherwise = abalance acct
       acct = ledgerAccount l a
-      name | Flat `elem` opts = a
+      name | Flat `elem` opts = accountNameDrop (dropFromOpts opts) a
            | otherwise        = depthspacer ++ partialname
       parents = parentAccountNames a
       interestingparents = filter (`elem` interestingaccts) parents

Hledger/Cli/Options.hs

@@ -76,6 +76,7 @@ options = [
  ,Option "E" ["empty"]        (NoArg  Empty)         "show empty/zero things which are normally elided"
  ,Option "R" ["real"]         (NoArg  Real)          "report only on real (non-virtual) transactions"
  ,Option ""  ["flat"]         (NoArg  Flat)          "balance report: show full account names, unindented"
+ ,Option ""    ["drop"]       (ReqArg Drop "N")     "balance report: with --flat, elide first N account name components"
  ,Option ""    ["no-total"]     (NoArg  NoTotal)       "balance report: hide the final total"
 -- ,Option "s" ["subtotal"]     (NoArg  SubTotal)      "balance report: show subaccounts"
  ,Option "W" ["weekly"]       (NoArg  WeeklyOpt)     "register report: show weekly summary"
@@ -115,6 +116,7 @@ data Opt =
     Empty | 
     Real | 
     Flat |
+    Drop   {value::String} |
     NoTotal |
     SubTotal |
     WeeklyOpt |
@@ -212,13 +214,20 @@ intervalFromOpts opts =
       periodopts   = reverse $ optValuesForConstructor Period opts
       intervalopts = reverse $ filter (`elem` [WeeklyOpt,MonthlyOpt,QuarterlyOpt,YearlyOpt]) opts
 
--- | Get the value of the (last) depth option, if any, otherwise a large number.
+-- | Get the value of the (last) depth option, if any.
 depthFromOpts :: [Opt] -> Maybe Int
 depthFromOpts opts = listtomaybeint $ optValuesForConstructor Depth opts
     where
       listtomaybeint [] = Nothing
       listtomaybeint vs = Just $ read $ last vs
 
+-- | Get the value of the (last) drop option, if any, otherwise 0.
+dropFromOpts :: [Opt] -> Int
+dropFromOpts opts = fromMaybe 0 $ listtomaybeint $ optValuesForConstructor Drop opts
+    where
+      listtomaybeint [] = Nothing
+      listtomaybeint vs = Just $ read $ last vs
+
 -- | Get the value of the (last) display option, if any.
 displayExprFromOpts :: [Opt] -> Maybe String
 displayExprFromOpts opts = listtomaybe $ optValuesForConstructor Display opts

MANUAL.markdown

@@ -282,13 +282,16 @@ Examples:
     $ hledger balance food -p 'last month'
 
 A final total is displayed, use `--no-total` to suppress this. Also, the
-`--depth` option shows accounts only to the specified depth, useful for an overview:
+`--depth N` option shows accounts only to the specified depth, useful for
+an overview:
 
     $ for y in 2006 2007 2008 2009 2010; do echo; echo $y; hledger -f $y.ledger balance ^expenses --depth 2; done
 
 With `--flat`, a non-hierarchical list of full account names is displayed
 instead. This mode shows just the accounts actually contributing to the
 balance, making the arithmetic a little more obvious to non-hledger users.
+In this mode you can also use `--drop N` to elide the first few account
+name components.
 
 ##### chart
 

hledger-lib/Hledger/Data/AccountName.hs

@@ -32,6 +32,9 @@ accountNameLevel :: AccountName -> Int
 accountNameLevel "" = 0
 accountNameLevel a = length (filter (==acctsepchar) a) + 1
 
+accountNameDrop :: Int -> AccountName -> AccountName
+accountNameDrop n = accountNameFromComponents . drop n . accountNameComponents
+
 -- | ["a:b:c","d:e"] -> ["a","a:b","a:b:c","d","d:e"]
 expandAccountNames :: [AccountName] -> [AccountName]
 expandAccountNames as = nub $ concatMap expand as