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, 16 insertions, 0 deletions

diff --git a/src/output.h b/src/output.h
index f0e7f9a5..a19c6235 100644
--- a/src/output.h
+++ b/src/output.h
@@ -64,6 +64,8 @@ protected:
   std::size_t prepend_width;
   xact_t *    last_xact;
   post_t *    last_post;
+  bool        first_report_title;
+  string      report_title;
 
 public:
   format_posts(report_t& _report, const string& format,
@@ -73,6 +75,10 @@ public:
     TRACE_DTOR(format_posts);
   }
 
+  virtual void title(const string& str) {
+    report_title = str;
+  }
+
   virtual void flush();
   virtual void operator()(post_t& post);
 
@@ -80,6 +86,8 @@ public:
     last_xact	 = NULL;
     last_post	 = NULL;
 
+    report_title = "";
+
     item_handler<post_t>::clear();
   }
 };
@@ -94,6 +102,8 @@ protected:
   format_t    prepend_format;
   std::size_t prepend_width;
   predicate_t disp_pred;
+  bool        first_report_title;
+  string      report_title;
 
   std::list<account_t *> posted_accounts;
 
@@ -108,6 +118,10 @@ public:
   std::pair<std::size_t, std::size_t>
   mark_accounts(account_t& account, const bool flat);
 
+  virtual void title(const string& str) {
+    report_title = str;
+  }
+
   virtual std::size_t post_account(account_t& account, const bool flat);
   virtual void	      flush();
 
@@ -117,6 +131,8 @@ public:
     disp_pred.mark_uncompiled();
     posted_accounts.clear();
 
+    report_title = "";
+
     item_handler<account_t>::clear();
   }
 };