subsequent rebuilds of notmuch always re-build sphinx and ruby

[David Bremner]

Daniel Kahn Gillmor <dkg at fifthhorseman.net> writes:

> On Mon 2019-04-22 21:03:05 -0300, David Bremner wrote:
>> There was a problem with the first patch, which I replaced with two more.
>
> thanks.  i've reviewed and published my review on that series.  I think
> it should probably be merged.
>
>> I'm open to ideas, but keep in mind we want to support parallel make,
>> which means we have to be careful not to trigger multiple invocations of
>> sphinx-build in parallel.

> hm, i'm not entirely sure why sphinx-build can't be run in parallel, if
> it could target the creation of specific files (but maybe it can't).

It can target specific files according to the documentation, but the
main issue is that it caches a bunch of state under
doc/_build/doctrees. It doesn't do any kind of locking, so multiple
writers leads to build failures.

>
> I do note that (independent of this series), if i run the following
> loop:
>
>
>      while make -j4 --trace; do
>         python3 -c 'print("="*100)'
>         touch doc/man1/notmuch-reply.rst
>      done
>
> then only every second run of make contains this info:
>

I think I see this also, but no idea yet what is going on.