Merge branch 'ds/ahead-behind'

"git for-each-ref" learns '%(ahead-behind:<base>)' that computes the
distances from a single reference point in the history with bunch
of commits in bulk.

* ds/ahead-behind:
  commit-reach: add tips_reachable_from_bases()
  for-each-ref: add ahead-behind format atom
  commit-reach: implement ahead_behind() logic
  commit-graph: introduce `ensure_generations_valid()`
  commit-graph: return generation from memory
  commit-graph: simplify compute_generation_numbers()
  commit-graph: refactor compute_topological_levels()
  for-each-ref: explicitly test no matches
  for-each-ref: add --stdin option

1 files changed, 14 insertions, 0 deletions

diff --git a/t/t6301-for-each-ref-errors.sh b/t/t6301-for-each-ref-errors.sh
index bfda1f46ad..2667dd13fe 100755
--- a/t/t6301-for-each-ref-errors.sh
+++ b/t/t6301-for-each-ref-errors.sh
@@ -54,4 +54,18 @@ test_expect_success 'Missing objects are reported correctly' '
 	test_must_be_empty brief-err
 '
 
+test_expect_success 'ahead-behind requires an argument' '
+	test_must_fail git for-each-ref \
+		--format="%(ahead-behind)" 2>err &&
+	echo "fatal: expected format: %(ahead-behind:<committish>)" >expect &&
+	test_cmp expect err
+'
+
+test_expect_success 'missing ahead-behind base' '
+	test_must_fail git for-each-ref \
+		--format="%(ahead-behind:refs/heads/missing)" 2>err &&
+	echo "fatal: failed to find '\''refs/heads/missing'\''" >expect &&
+	test_cmp expect err
+'
+
 test_done