t6600: add test cases for side-exhaustion edge cases

Add test cases to t6600-test-reach.sh that exercise edge cases in the
side-exhaustion optimization for paint_down_to_common():

 - in_merge_bases_many:self: commit is both A and one of the X inputs
 - get_merge_bases_many:duplicate-twos: duplicate entries in X list
 - get_merge_bases_many:pending-stale: STALE transition on an
   already-painted commit (ps-* diamond topology)
 - get_merge_bases_many:infinity-both-sides: both tips outside the
   commit-graph with non-monotonic dates (pi-* topology)

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Kristofer Karlsson <krka@spotify.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/t6600-test-reach.sh b/t/t6600-test-reach.sh
index b5b314e57068f9732c33f93895ab45684cad4e0b..c2e091aad11a6dbbb2c7411ebbf3cb4beedf50e7 100755 (executable)
--- a/t/t6600-test-reach.sh
+++ b/t/t6600-test-reach.sh
@@ -49,6 +49,62 @@ test_expect_success 'setup' '
                        git tag -a -m "$x-$i" tag-$x-$i commit-$x-$i || return 1
                done
        done &&
+
+       # Build a small side topology to exercise the (PARENT1|PARENT2) ->
+       # (PARENT1|PARENT2|STALE) transition in paint_down_to_common(); the
+       # 10x10 grid above does not exercise it because no merge-base candidate
+       # there is a descendant of another, so STALE never reaches a
+       # still-pending candidate.
+       #
+       #       ps-X
+       #       /|\
+       #      / | \
+       #   ps-Z ps-B ps-W
+       #     |  / \  |
+       #     | /   \ |
+       #     |/     \|
+       #   ps-T1   ps-T2
+       #
+       # where ps-T1=merge(ps-Z,ps-B), ps-T2=merge(ps-W,ps-B), so
+       # merge-base(ps-T1,ps-T2) = ps-B. During the walk, ps-X transitions
+       # to (PARENT1|PARENT2) via ps-Z and ps-W before ps-B is dequeued;
+       # then the STALE-walk from ps-B transitions ps-X to
+       # (PARENT1|PARENT2|STALE).
+       git checkout --orphan ps-orphan &&
+       test_commit ps-X &&
+       git checkout -b ps-B-br ps-X && test_commit ps-B &&
+       git checkout -b ps-Z-br ps-X && test_commit ps-Z &&
+       git checkout -b ps-W-br ps-X && test_commit ps-W &&
+       git checkout -b ps-T1 ps-Z &&
+       git merge --no-ff -m ps-T1 ps-B &&
+       git checkout -b ps-T2 ps-W &&
+       git merge --no-ff -m ps-T2 ps-B &&
+
+       # Build a side topology that lives entirely outside the half
+       # commit-graph and has non-monotonic commit dates, to exercise the
+       # INFINITY-gate in paint_down_to_common. With both tips outside
+       # the graph, generation is INFINITY and the queue falls back to
+       # commit-date order, which here is non-monotonic.
+       #
+       #   pi-X (date 500, PARENT1 tip) --> pi-P, pi-D
+       #   pi-D (date 480) --> pi-C
+       #   pi-C (date 200) --> pi-B
+       #   pi-B (date 100, PARENT2 tip) --> pi-P
+       #   pi-P (date 450, root)
+       #
+       # merge-base(pi-X, pi-B) = pi-B (it is an ancestor of pi-X and is
+       # itself one of the queried tips).
+       git checkout --orphan pi-orphan &&
+       test_commit --date "@450 +0000" pi-P &&
+       test_commit --date "@100 +0000" pi-B &&
+       test_commit --date "@200 +0000" pi-C &&
+       test_commit --date "@480 +0000" pi-D &&
+       GIT_AUTHOR_DATE="@500 +0000" GIT_COMMITTER_DATE="@500 +0000" \
+               git commit-tree -p pi-D -p pi-P -m pi-X pi-D^{tree} >pi-X-oid &&
+       pi_x="$(cat pi-X-oid)" &&
+       git branch -f pi-X-br "$pi_x" &&
+       git tag pi-X "$pi_x" &&
+
        git commit-graph write --reachable &&
        mv .git/objects/info/commit-graph commit-graph-full &&
        chmod u+w commit-graph-full &&
@@ -146,6 +202,16 @@ test_expect_success 'in_merge_bases_many:miss-heuristic' '
        test_all_modes in_merge_bases_many
 '
 
+test_expect_success 'in_merge_bases_many:self' '
+       cat >input <<-\EOF &&
+       A:commit-6-8
+       X:commit-5-9
+       X:commit-6-8
+       EOF
+       echo "in_merge_bases_many(A,X):1" >expect &&
+       test_all_modes in_merge_bases_many
+'
+
 test_expect_success 'is_descendant_of:hit' '
        cat >input <<-\EOF &&
        A:commit-5-7
@@ -183,6 +249,51 @@ test_expect_success 'get_merge_bases_many' '
        test_all_modes get_merge_bases_many
 '
 
+test_expect_success 'get_merge_bases_many:duplicate-twos' '
+       cat >input <<-\EOF &&
+       A:commit-5-7
+       X:commit-4-8
+       X:commit-4-8
+       X:commit-6-6
+       X:commit-6-6
+       X:commit-8-3
+       EOF
+       {
+               echo "get_merge_bases_many(A,X):" &&
+               git rev-parse commit-5-6 \
+                             commit-4-7 | sort
+       } >expect &&
+       test_all_modes get_merge_bases_many
+'
+
+test_expect_success 'get_merge_bases_many:pending-stale' '
+       # Exercises the (PARENT1|PARENT2) -> (...|STALE) transition path in
+       # paint_down_to_common(). See the topology comment in the setup test.
+       cat >input <<-\EOF &&
+       A:ps-T1
+       X:ps-T2
+       EOF
+       {
+               echo "get_merge_bases_many(A,X):" &&
+               git rev-parse ps-B
+       } >expect &&
+       test_all_modes get_merge_bases_many
+'
+
+test_expect_success 'get_merge_bases_many:infinity-both-sides' '
+       # Exercises the push-time INFINITY-gate in paint_down_to_common(). See
+       # the pi-* topology comment in the setup test.
+       cat >input <<-\EOF &&
+       A:pi-X
+       X:pi-B
+       EOF
+       {
+               echo "get_merge_bases_many(A,X):" &&
+               git rev-parse pi-B
+       } >expect &&
+       test_all_modes get_merge_bases_many
+'
+
 test_expect_success 'reduce_heads' '
        cat >input <<-\EOF &&
        X:commit-1-10