daterange: support relative terms

Support relative terms when writing date ranges in the search and filter
commands with the -d flag. Syntax is inspired by the notmuch search
terms.

Terms can be written with spaces or underscores for a better
readability, so both "this_week" and "this week" are allowed. Terms are
not case-sensitive.

Some terms can be prefixed with either "this" or "last" where applicable
("this" is assumed by default if omitted):

- "today", "yesterday"
- ("this"|"last") "year", "month", "week"
- all weekdays (e.g. "Tuesday", "last_wed")
- all months  (e.g. "January", "last_feb")

Note that "month" should always be spelled out to prevent a possible
ambiguity with "Monday".

Weekdays and months do not need to be written out completely, i.e.
"February..March" and "Feb..Mar" are both understood.

Relative date terms can be used with the <N (year|month|week|day)>
syntax where N is a positive integer indicating the number of time units
in the past from today. The units can be abbreviated with a single
letter, e.g. "1w 1d.." is the same as "1 week 1 day..".

More examples:
:filter -d yesterday
:filter -d last_monday..
:filter -d mon..sat
:filter -d 1y1m1w1d..
:search -d this_week "PATCH aerc"

Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

1 files changed, 19 insertions, 0 deletions

diff --git a/doc/aerc-search.1.scd b/doc/aerc-search.1.scd
index 51e93ade..8349874b 100644
--- a/doc/aerc-search.1.scd
+++ b/doc/aerc-search.1.scd
@@ -44,6 +44,25 @@ aerc-search - search and filter patterns and options for *aerc*(1)
 		Search for messages within a particular date range defined as
 		\[start, end) where the dates are in the YYYY-MM-DD format.
 
+		Relative dates can be used to specify a date range. Spaces and
+		underscores are allowed to improve readability:
+
+		*today*, *yesterday*
+
+		*(this|last) (year|month|week)*
+
+		*Weekdays*, *Monthnames*
+			Can also be abbreviate, so Monday..Tuesday can written
+			as Mon..Tue and February..March as Feb..Mar.
+
+		_<N>_ *(y[ear]|m[onth]|w[eek]|d[ay])*
+			_<N>_ is a positive integer that represents the number
+			of the time units in the past. Mutiple relative terms
+			can will be accumulated. The units can also be
+			abbreviated by a single letter such that yesterday would
+			correspond to _1d_ (equivalent to _1 day_ or _1_day_)
+			and _8 days ago_ would be either _1w1d_ or _8d_.
+
 # NOTMUCH
 
 *search* _query_...