Many color per line in notuch emacs mode

[kedals0 at gmail.com]

Hi,

I can set color per line using notmuch-search-line-faces. But I would
like to specify color per line field, i.e a color for date, another for
authors for exemple.

To do this, I would like to use a 3-tuple list for
notmuch-search-line-faces:
:type '(alist :key-type (string) :field (string) :value-type
(custom-face-edit))

The problem is function notmuch-search-color-line take a non structured
line in args. Then it is needed to parse it to find out field.

Do you think it would be possible to add a mecanism which permit to
color a field during line building ?

Thx,
Dal