[RFC] lib: add support for date:<query>..! to mean date:<query>..<query>

[Jani Nikula]

Up to debate:

1) Is something like this useful at all as an intermediate step before
we can have support for date:<query>? (This can be done with a future
version of Xapian, or with a custom query query parser.)

2) If yes, are there better alternatives to "!" as the end point? (Or
should the special case be the start point?) Also "@" and "same" have
been suggested. Examples: date:yesterday..! date:today..@
date:@..monday date:january..same.

Idea from Mark Walters <markwalters1009 at gmail.com>.
---
 lib/parse-time-vrp.cc    | 5 +++++
 test/T500-search-date.sh | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/lib/parse-time-vrp.cc b/lib/parse-time-vrp.cc
index 33f07db3410e..03804cf50fa8 100644
--- a/lib/parse-time-vrp.cc
+++ b/lib/parse-time-vrp.cc
@@ -31,6 +31,7 @@ Xapian::valueno
 ParseTimeValueRangeProcessor::operator() (std::string &begin, std::string &end)
 {
     time_t t, now;
+    std::string b;
 
     /* Require date: prefix in start of the range... */
     if (STRNCMP_LITERAL (begin.c_str (), PREFIX))
@@ -38,6 +39,7 @@ ParseTimeValueRangeProcessor::operator() (std::string &begin, std::string &end)
 
     /* ...and remove it. */
     begin.erase (0, sizeof (PREFIX) - 1);
+    b = begin;
 
     /* Use the same 'now' for begin and end. */
     if (time (&now) == (time_t) -1)
@@ -51,6 +53,9 @@ ParseTimeValueRangeProcessor::operator() (std::string &begin, std::string &end)
     }
 
     if (!end.empty ()) {
+	if (end == "!" && ! b.empty ())
+	    end = b;
+
 	if (parse_time_string (end.c_str (), &t, &now, PARSE_TIME_ROUND_UP_INCLUSIVE))
 	    return Xapian::BAD_VALUENO;
 
diff --git a/test/T500-search-date.sh b/test/T500-search-date.sh
index 70bcf344b4f7..18a47b114fa9 100755
--- a/test/T500-search-date.sh
+++ b/test/T500-search-date.sh
@@ -8,6 +8,10 @@ test_begin_subtest "Absolute date range"
 output=$(notmuch search date:2010-12-16..12/16/2010 | notmuch_search_sanitize)
 test_expect_equal "$output" "thread:XXX   2010-12-16 [1/1] Olivier Berger; Essai accentué (inbox unread)"
 
+test_begin_subtest "Absolute date range with 'same' operator"
+output=$(notmuch search date:2010-12-16..! | notmuch_search_sanitize)
+test_expect_equal "$output" "thread:XXX   2010-12-16 [1/1] Olivier Berger; Essai accentué (inbox unread)"
+
 test_begin_subtest "Absolute time range with TZ"
 notmuch search date:18-Nov-2009_02:19:26-0800..2009-11-18_04:49:52-06:00 | notmuch_search_sanitize > OUTPUT
 cat <<EOF >EXPECTED
-- 
2.1.4