Looking at the definition of `org-agenda-timerange-leaders' suggests
that the second item of the list can be a function.
(defcustom org-agenda-timerange-leaders '("" "(%d/%d): ")
"Text preceding timerange entries in the agenda view.
This is a list with two strings. The first applies when the range
is entirely on one day. The second applies if the range spans several days.
The strings may have two \"%d\" format specifiers which will be filled
with the sequence number of the days, and the total number of days in the
range, respectively."
:group 'org-agenda-line-format
:type '(list
(string :tag "Deadline today ")
(choice :tag "Deadline relative"
(string :tag "Format string")
(function))))
^^^
However, setting it to a function simply yields a type error since
`format' expects a string. This has been a problem ever since the
option was introduced in the commit ea258dbdb.
It would be nice if org could accept a function, as one would expect
from the definition of the concerned option. The function would accept two
arguments and return a format-string or a _formatted_ string?
Regards.
P.S. Please add me to CCs since I don't follow the mailing list.
