b4 send removes newlines from cover-letter

[floatious]

Hello there,

Sometimes there is a value in having two empty lines in a cover-letter,
to more clearly separate certain paragraphs from other paragraphs.

Looking at the empty commit that contains the cover-letter, in e.g.:
floatious/linux@3be58ac

I can see that the cover-letter has two empty newlines in certain places, as intended.

However, if I look at the cover-letter that was actually sent to the list:
https://lore.kernel.org/linux-pci/20240424-rockchip-pcie-ep-v1-v1-0-b1a02ddad650@kernel.org/

We can see that it has actually stripped the second empty line, in the cases where there were
more than a single empty line. (With the result being that the cover-letter is harder to read IMO.)

If would be nice if b4 send did not strip newlines, or if nothing else, there could be an option to
not strip newlines.

[mricon]

This is the side-effect of code that handles removing comments from the cover letter. E.g. consider the following contents:

This is the cover letter introduction 
paragraph

# Removed because this person is a secret agent
# Removed-trailer: Some Person <some.person@example.com>

Signed-off-by: My Self <...>

When we remove the comments, we end up with a double newline, that was most likely not intentional. So, we collapse all repeated newlines into a single one. I'll think about how we can recognize intentional double newlines, but it's not a simple change.