Add rudimentary date-based search.

The rudimentary aspect here is that the date ranges are specified with
UNIX timestamp values (number of seconds since 1970-01-01 UTC). One
thing that can help here is using the date program to determins
timestamps, such as:

	$(date +%s -d 2009-10-01)..$(date +%s)

Long-term, we'll probably need to do our own query parsing to be able
to support directly-specified dates and also relative expressions like
"since:'2 months ago'".

1 files changed, 16 insertions, 1 deletions

diff --git a/notmuch.c b/notmuch.c
index 72ca6204..24f87288 100644
--- a/notmuch.c
+++ b/notmuch.c
@@ -89,7 +89,22 @@ static const char search_terms_help[] =
     "\t\tParentheses can also be used to control the combination of\n"
     "\t\tthe Boolean operators, but will have to be protected from\n"
     "\t\tinterpretation by the shell, (such as by putting quotation\n"
-    "\t\tmarks around any parenthesized expression).\n\n";
+    "\t\tmarks around any parenthesized expression).\n"
+    "\n"
+    "\t\tFinally, results can be restricted to only messages within a\n"
+    "\t\tparticular time range, (based on the Date: header) with:\n"
+    "\n"
+    "\t\t\t<intial-timestamp>..<final-timestamp>\n"
+    "\n"
+    "\t\tEach timestamp is a number representing the number of seconds\n"
+    "\t\tsince 1970-01-01 00:00:00 UTC. This is not the most convenient\n"
+    "\t\tmeans of expressing date ranges, but until notmuch is fixed to\n"
+    "\t\taccept a more convenient form, one can use the date program to\n"
+    "\t\tconstruct timestamps. For example, with the bash shell the\n"
+    "\t\tfollowing syntax would specify a date range to return messages\n"
+    "\t\tfrom 2009-10-01 until the current time:\n"
+    "\n"
+    "\t\t\t$(date +%s -d 2009-10-01)..$(date +%s)\n\n";
 
 command_t commands[] = {
     { "setup", notmuch_setup_command,