Currently the tools/build-docs was slow
because the clean option was rebulding everything.
But this is only required if one wants the left
sidebar to update.
So now set the default to exclude clean and
add clean option only if --clean is passed.
Also a warning is displayed if clean option is
not passed that the left sidebar won't update.
Fixes#17961.
Change the script to python. This is done
for the following reasons.
* It enables us to use the sanity_check.
* Later when we add warning to include
--clean flag we can use the pre-existing
WARNING from zulip_tools rather than using
terminal color codes.
TODO: Currently this script is slow as the
clean option is expensive so instead use only
html by default and clean only if --clean
option is passed.
Part of #17961.
In tools/build-docs line 3:
cd "$(dirname "$0")"/../docs
^-- SC2164: Use 'cd ... || exit' or 'cd ... || return' in case cd fails.
Signed-off-by: Anders Kaseorg <andersk@mit.edu>