Added --date, similar to --account and --payee

This lets you do things like store a date as the value of a tag, then
run:

  ledger --date='has_tag("Foo") ? to_date(tag("Foo")) : date' reg

1 files changed, 8 insertions, 3 deletions

diff --git a/src/filters.cc b/src/filters.cc
index 4b54a0cd..8c5d099e 100644
--- a/src/filters.cc
+++ b/src/filters.cc
@@ -706,22 +706,27 @@ void transfer_details::operator()(post_t& post)
   temp.set_state(post.state());
 
   bind_scope_t bound_scope(scope, temp);
+  value_t      substitute(expr.calc(bound_scope));
 
   switch (which_element) {
-  case SET_PAYEE:
-    xact.payee = expr.calc(bound_scope).to_string();
+  case SET_DATE:
+    xact.set_date(substitute.to_date());
     break;
 
   case SET_ACCOUNT: {
     std::list<string> account_names;
     temp.account->remove_post(&temp);
-    split_string(expr.calc(bound_scope).to_string(), ':', account_names);
+    split_string(substitute.to_string(), ':', account_names);
     temp.account = create_temp_account_from_path(account_names, temps,
 						 xact.journal->master);
     temp.account->add_post(&temp);
     break;
   }
 
+  case SET_PAYEE:
+    xact.payee = substitute.to_string();
+    break;
+
   default:
     assert(false);
     break;