bug#33699: Multi-component paths ignored by --{exclude, include}-dir ?

[Lyude Paul]

Hi! Sorry for bugging you, but I noticed something a little peculiar about
grep that I wasn't expecting, and I'm not sure if this is a bug or not.
I've been trying to use grep in one of my scripts to exclude files from
any directories starting with Documentation/output using --exclude-dir.
Example:

grep vcpi_ . -rl --exclude-dir Documentation/output

However, this doesn't seem to work at all as it returns:

./Module.symvers
./drivers/gpu/drm/radeon/radeon_dp_mst.c
./drivers/gpu/drm/drm_dp_mst_topology.c
./drivers/gpu/drm/nouveau/dispnv50/disp.c
./drivers/gpu/drm/nouveau/nvkm/engine/disp/rootnv50.c
./drivers/gpu/drm/nouveau/include/nvif/cl5070.h
./drivers/gpu/drm/Module.symvers
./drivers/gpu/drm/i915/intel_dp_mst.c
./drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
./include/drm/drm_dp_mst_helper.h
./Documentation/output/gpu/drm-kms-helpers.html
./Documentation/output/gpu/drm-dp-mst-helpers.html
./Documentation/output/gpu/dp-mst.html
./Documentation/output/genindex.html
./Documentation/output/latex/gpu.aux
./Documentation/output/latex/gpu.tex
./Documentation/output/searchindex.js

I would have thought maybe this could be worked around by using
--exclude instead:

grep vcpi_ . -rl --exclude '.*Documentation/output.*'

But the result is the same. Is this intentional, or an actual bug?
Either way, at the very least it seems like something that should be
clarified in the man page.
-- 
Cheers,
        Lyude Paul