On Sun, Feb 23, 2020 at 11:47:32PM -0500, Jeff King wrote:

One thing that compels me is the recent report that we still build with
common crypto by default on macOS, which was definitely _not_ intended.
That's a bug that can be fixed, but it wouldn't have happened in the
first place if we only supported sha1dc.

I just noticed you were the original reporter there, too. So I guess it
compelled you, too. ;)

If we do want to keep the other implementations around, another thing
that might be worth doing is to teach t0013 to complain when the
collision-detecting sha1 is not in use (i.e., rather than auto-skipping
when built without DC_SHA1, require the user to set a special
NO_REALLY_I_CHOOSE_NOT_TO_USE_DC_SHA1_AND_AM_AWARE_OF_THE_IMPLICATIONS
variable). That would provide a cross-check on the build flags.

-Peff