[PATCH v2 2/5] Makefile: under "make dist", include the sha1collisiondetection submodule

Include the sha1collisiondetection submodule when running "make dist". Even though we've been shipping the sha1collisiondetection submodule[1] and using it by default if it's checked out[2] anyone downloading git as a tarball would just get an empty sha1collisiondetection/ directory.

Doing this automatically is a feature that's missing from git-archive, but in the meantime let's bundle this up into the tarball we ship. This ensures that the DC_SHA1_SUBMODULE flag does what's intended even in an unpacked tarball, and more importantly means we're building the exact same code from the same paths from git.git and from the tarball.

I am not including all the files in the submodule, only the ones git actually needs (and the licenses), only including some files like this would be a useful feature if git-archive ever adds the ability to bundle up submodules.

1. commit 86cfd61e6b ("sha1dc: optionally use sha1collisiondetection
   as a submodule", 2017-07-01)
2. cac87dc01d ("sha1collisiondetection: automatically enable when
   submodule is populated", 2017-07-01)

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 Makefile | 15 +++++++++++++++
 1 file changed, 15 insertions(+)