test "$(git rev-parse refs/notes/x)" = "$(git rev-parse refs/notes/y)"
'
+test_expect_success 'merge empty notes ref (z => y)' '
+ # Prepare empty (but valid) notes ref (z)
+ git config core.notesRef refs/notes/z &&
+ git notes add -m "foo" &&
+ git notes remove &&
+ git notes >output_notes_z &&
+ test_cmp /dev/null output_notes_z &&
+ # Do the merge (z => y)
+ git config core.notesRef refs/notes/y &&
+ git notes merge z &&
+ verify_notes y &&
+ # y should no longer point to the same notes commit as x
+ test "$(git rev-parse refs/notes/x)" != "$(git rev-parse refs/notes/y)"
+'
+
+cat <<EOF | sort >expect_notes_y
+0f2efbd00262f2fd41dfae33df8765618eeacd99 $commit_sha5
+dec2502dac3ea161543f71930044deff93fa945c $commit_sha4
+4069cdb399fd45463ec6eef8e051a16a03592d91 $commit_sha3
+d000d30e6ddcfce3a8122c403226a2ce2fd04d9d $commit_sha2
+43add6bd0c8c0bc871ac7991e0f5573cfba27804 $commit_sha1
+EOF
+
+cat >expect_log_y <<EOF
+$commit_sha5 5th
+Notes on 5th commit
+
+$commit_sha4 4th
+New notes on 4th commit
+
+$commit_sha3 3rd
+Notes on 3rd commit
+
+More notes on 3rd commit
+
+$commit_sha2 2nd
+New notes on 2nd commit
+
+$commit_sha1 1st
+Notes on 1st commit
+
+More notes on 1st commit
+
+EOF
+
+test_expect_success 'change notes on other notes ref (y)' '
+ # Append to 1st commit notes
+ git notes append -m "More notes on 1st commit" 1st &&
+ # Add new notes to 2nd commit
+ git notes add -m "New notes on 2nd commit" 2nd &&
+ verify_notes y
+'
+
+cat <<EOF | sort >expect_notes_x
+0f2efbd00262f2fd41dfae33df8765618eeacd99 $commit_sha5
+1f257a3a90328557c452f0817d6cc50c89d315d4 $commit_sha4
+daa55ffad6cb99bf64226532147ffcaf5ce8bdd1 $commit_sha1
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 5th
+Notes on 5th commit
+
+$commit_sha4 4th
+New notes on 4th commit
+
+More notes on 4th commit
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+
+$commit_sha1 1st
+Notes on 1st commit
+
+EOF
+
+test_expect_success 'change notes on notes ref (x)' '
+ git config core.notesRef refs/notes/x &&
+ git notes remove 3rd &&
+ git notes append -m "More notes on 4th commit" 4th &&
+ verify_notes x
+'
+
+cat <<EOF | sort >expect_notes_x
+0f2efbd00262f2fd41dfae33df8765618eeacd99 $commit_sha5
+1f257a3a90328557c452f0817d6cc50c89d315d4 $commit_sha4
+d000d30e6ddcfce3a8122c403226a2ce2fd04d9d $commit_sha2
+43add6bd0c8c0bc871ac7991e0f5573cfba27804 $commit_sha1
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 5th
+Notes on 5th commit
+
+$commit_sha4 4th
+New notes on 4th commit
+
+More notes on 4th commit
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+New notes on 2nd commit
+
+$commit_sha1 1st
+Notes on 1st commit
+
+More notes on 1st commit
+
+EOF
+
+test_expect_success 'merge y into x => Non-conflicting 3-way merge' '
+ git notes merge y &&
+ verify_notes x &&
+ verify_notes y
+'
+
+cat <<EOF | sort >expect_notes_w
+05a4927951bcef347f51486575b878b2b60137f2 $commit_sha3
+d000d30e6ddcfce3a8122c403226a2ce2fd04d9d $commit_sha2
+EOF
+
+cat >expect_log_w <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+
+$commit_sha3 3rd
+New notes on 3rd commit
+
+$commit_sha2 2nd
+New notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'create notes on new, separate notes ref (w)' '
+ git config core.notesRef refs/notes/w &&
+ # Add same note as refs/notes/y on 2nd commit
+ git notes add -m "New notes on 2nd commit" 2nd &&
+ # Add new note on 3rd commit (non-conflicting)
+ git notes add -m "New notes on 3rd commit" 3rd &&
+ # Verify state of notes on new, separate notes ref (w)
+ verify_notes w
+'
+
+cat <<EOF | sort >expect_notes_x
+0f2efbd00262f2fd41dfae33df8765618eeacd99 $commit_sha5
+1f257a3a90328557c452f0817d6cc50c89d315d4 $commit_sha4
+05a4927951bcef347f51486575b878b2b60137f2 $commit_sha3
+d000d30e6ddcfce3a8122c403226a2ce2fd04d9d $commit_sha2
+43add6bd0c8c0bc871ac7991e0f5573cfba27804 $commit_sha1
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 5th
+Notes on 5th commit
+
+$commit_sha4 4th
+New notes on 4th commit
+
+More notes on 4th commit
+
+$commit_sha3 3rd
+New notes on 3rd commit
+
+$commit_sha2 2nd
+New notes on 2nd commit
+
+$commit_sha1 1st
+Notes on 1st commit
+
+More notes on 1st commit
+
+EOF
+
+test_expect_success 'merge w into x => Non-conflicting history-less merge' '
+ git config core.notesRef refs/notes/x &&
+ git notes merge w &&
+ # Verify new state of notes on other notes ref (x)
+ verify_notes x &&
+ # Also verify that nothing changed on other notes refs (y and w)
+ verify_notes y &&
+ verify_notes w
+'
+
test_done