##13:40 Saturday 01 November 2014 JST##
I’ve installed Prelude Emacs, hoping that it will support my desire to easily embed images in my journal entries. To insert an image, I need to insert soemthing like this:

The idea is that I type some keys, in this case C-x !
and I
interactively am asked for the alt text and then can quickly get a
list of images based on the year/month of my current journal entry, in
this case 2014/11.
Based on hakyll.el, I got the first part sorted:
(defun hakyll-insert-image (alt-text)
"Insert an image from /images/yyyy/mm to current buffer /posts/yyyy/mm/dd/....md"
(interactive "sAltText: ")
(let ((current-buffer-filename (buffer-file-name)))
(insert
(format ""
alt-text
current-buffer-filename
))
)
)
So instead of inserting the current buffer filename, I want to parse
the current buffer filename for yyyy/mm
and then select a file
from ~/journal/images/yyyy/mm
and insert (part of) its name instead.