Customising fill-paragrah

[Sebastian Tennant]

Hi All,

I'd like to be able to fill (M-q) a paragraph that begins with a colon
(in column 0) followed by three SPC chars, without it reducing the three
spaces to one, i.e., so that I can type M-q on the example para below
without it having any affect.

:   lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem
    ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum

Also, the indentation of the second line is preserved (once it is set) but
it would be nice to have fill-paragraph automatically indent the second
line by four spaces (in auto-fill-mode) if the first line begins with a
colon.

Any tips/advice/suggestions/pointers much appreciated.

Sebastian
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