New: --group-by=EXPR and --group-title-format=FMT

The --group-by option allows for most reports to be split up into
sections based on the varying value of EXPR.  For example, to see
register subtotals by payee, use:

  ledger reg --group-by=payee -s

This works for separated balances too:

  ledger bal --group-by=payee

Another interesting possibility is seeing a register of all the accounts
affected by a related account:

  ledger reg -r --group-by=payee

The option --group-title-format can be used to add a separator bar to
the group titles.  The option --no-titles can be used to drop titles
altogether.

1 files changed, 10 insertions, 0 deletions

diff --git a/src/print.h b/src/print.h
index f323b153..5263ec91 100644
--- a/src/print.h
+++ b/src/print.h
@@ -62,6 +62,7 @@ protected:
   xacts_present_map xacts_present;
   xacts_list	    xacts;
   bool		    print_raw;
+  bool		    first_title;
 
 public:
   print_xacts(report_t& _report, bool _print_raw = false);
@@ -69,8 +70,17 @@ public:
     TRACE_DTOR(print_xacts);
   }
 
+  virtual void title(const string&);
+
   virtual void flush();
   virtual void operator()(post_t& post);
+
+  virtual void clear() {
+    xacts_present.clear();
+    xacts.clear();
+
+    item_handler<post_t>::clear();
+  }
 };