Re: [PATCH 1/3] checkout: describe_detached_head: remove 3dots after committish

Thanks for all the feedback provided!

I'd like to summarise what consensus we have reached so far and
then propose a way forward:

   * we'll use the term "ellipsis (pl. ellipses)" for what's
     been referred to as "3dots", "n-dots", "many dots" and so
     forth

   * we would like to use ellipses when attached to SHA-1
     values only for the purpose of specifying a symmetric
     difference (as per gitrevisions(7))

   * the usage of ellipses as a "here we truncated something
     longer" is a relic which should be phased out

To get there, preventing describe_detached_head from appending
an ellipsis to the SHA-1 values it prints is one important step.

This change does not cause any test to fall over.

The other important step is dealing with the "git diff --raw"
output which features ellipses in the relic-fashion no longer
desired.

It would appear that simplifying diff.c's diff_aligned_abbrev
routine to something like:

	/* Do we want all 40 hex characters?
	 */
	if (len == GIT_SHA1_HEXSZ)
		return oid_to_hex(oid);

	/* An abbreviated value is fine.
	 */
	return diff_abbrev_oid(oid, len);

does do the trick.

This change causes quite a few tests to fall over; however, they
all have truncated-something-longer-ellipses in their
raw-diff-output expected sections, and removing the ellipses
from there makes the tests pass again, :-)

If we can agree that this is a way forward, i'll create & send
v2 of the patch series to the mailing list (it'll include the
fixed tests) and we'll see where we go from there.