I'm having a look at this, and figured out that the /usr/share/doc/README.html on the deb package almost certainly comes from the ./MANUAL.html file on the rclone source tree (the fact that they are byte-by-byte identical is a big clue ), and from the ./Makefile I can determine the latter comes from ./MANUAL.md.
But I can't find how the deb package gets generated (including the MANUAL.html file being renamed as README.html to be placed in it). Is the deb file generation code ´outside' the rclone source tree, or am I missing something?
Thanks @Darthshadow, the chance of finding that by myself would have been almost infinitesimal...
EDIT: FWIW, what I was actually trying to find (ie, how ./MANUAL.html on the source tree turns into /usr/share/doc/rclone/README.html in the DEB file) is at