Patrick Steinhardt [off-list ref] writes:

There has recently been some discussion around how C preprocessor
directives shall be indented [1]. This discussion was settled towards
indenting after the hash by two spaces [2]. Document it as such.

It was settled to have space after and not before the hash, but I do
not recall ever agreeing to two spaces.  I prefer to increment by 1
for each level instead to keep the whole thing less distracting
while carrying meaningful information.

Thanks.