[O] History list for %^{...} in capture

[Phil Hudson]

Arising from a discussion here a couple of weeks ago, I'm thinking about
how best to add a history list to org-capture's current
%^{prompt|default|choice2|...|choiceN} escape syntax. Here's my thinking
so far.

%^{prompt|'histList}
%^{prompt|default|'histList}
%^{prompt|default|choiceToPrepend|...|'histList|choiceToAppend|...}

Note the quote distinguishing the variable name.

Effectively the third example means: merge choices "default" and
"choiceTo*" into 'histList, prepending or appending each choice (if it
is not already an element of `histList') according to whether it occurs
before or after 'histList. Usually we would not expect prepending and
appending, just the prompt, default and history list as in the second
example. However, this form might be useful for pre-populating an
otherwise empty list.

I've identified the place in the code where the changes would need to be
coded, but I thought I should get your ideas before I dive in.
Effectively something similar is being done behind the scenes already
and then discarded; I would just be bringing it into the light of day
and making it persistent across calls.

WDYT? Good idea? Too complex? Too "busy"? Useful? Not useful?

-- 
Phil Hudson                   http://hudson-it.ddns.net
@UWascalWabbit                 PGP/GnuPG ID: 0x887DCA63