[PATCH 0/4] SHA1DC fixes & fully moving to a git.git submodule

We've now had a couple of Git releases where we've used sha1collisiondetection/ if it's checked out, but have gracefully fallen back on sha1dc/ if it's not there.

This series makes it a hard requirement, without 4/4 you'll still be able to do NO_DC_SHA1_SUBMODULE=UnfortunatelyYes, but with it even the ability to do that is removed, i.e. we're fully on the submodule (unless you have it as an external library).

1/4 should be destined straight for inclusion since it's a bugfix to the existing logic, and 2/4 could tag along with it, but none of this is urgent, so I'd figured I'd sent it all as one series and see what people think.

Ævar Arnfjörð Bjarmason (4):
  Makefile: don't error out under DC_SHA1_EXTERNAL if
    DC_SHA1_SUBMODULE=auto
  sha1dc_git.h: re-arrange an ifdef chain for a subsequent change
  Makefile: use the sha1collisiondetection submodule by default
  sha1dc: remove in favor of using sha1collisiondetection as a submodule

 Makefile              |   29 +-
 sha1dc/.gitattributes |    1 -
 sha1dc/LICENSE.txt    |   30 -
 sha1dc/sha1.c         | 1900 -------------------------------------------------
 sha1dc/sha1.h         |  110 ---
 sha1dc/ubc_check.c    |  372 ----------
 sha1dc/ubc_check.h    |   52 --
 sha1dc_git.h          |    6 +-
 8 files changed, 14 insertions(+), 2486 deletions(-)
 delete mode 100644 sha1dc/.gitattributes
 delete mode 100644 sha1dc/LICENSE.txt
 delete mode 100644 sha1dc/sha1.c
 delete mode 100644 sha1dc/sha1.h
 delete mode 100644 sha1dc/ubc_check.c
 delete mode 100644 sha1dc/ubc_check.h