reflog tests: add --updateref tests

Add tests that cover blindspots in "git reflog delete --updateref"
behavior. Before this change removing the "type & REF_ISSYMREF" check
added in 5e6f003ca8a (reflog_expire(): ignore --updateref for symbolic
references, 2015-03-03) would not fail any tests.

The "--updateref" option was added in 55f10565371 (git-reflog: add
option --updateref to write the last reflog sha1 into the ref,
2008-02-22) for use in git-stash.sh, see e25d5f9c82e (git-stash: add
new 'drop' subcommand, 2008-02-22).

Even though the regression test I need is just the "C" case here,
let's test all these combinations for good measure. I started out
doing these as a for-loop, but I think this is more readable.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/t1417-reflog-updateref.sh b/t/t1417-reflog-updateref.sh
new file mode 100755 (executable)
index 0000000..14f13b5
--- /dev/null
+++ b/t/t1417-reflog-updateref.sh
@@ -0,0 +1,65 @@
+#!/bin/sh
+
+test_description='git reflog --updateref'
+
+TEST_PASSES_SANITIZE_LEAK=true
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+       git init -b main repo &&
+       (
+               cd repo &&
+
+               test_commit A &&
+               test_commit B &&
+               test_commit C &&
+
+               cp .git/logs/HEAD HEAD.old &&
+               git reset --hard HEAD~ &&
+               cp HEAD.old .git/logs/HEAD
+       )
+'
+
+test_reflog_updateref () {
+       exp=$1
+       shift
+       args="$@"
+
+       test_expect_success REFFILES "get '$exp' with '$args'"  '
+               test_when_finished "rm -rf copy" &&
+               cp -R repo copy &&
+
+               (
+                       cd copy &&
+
+                       $args &&
+                       git rev-parse $exp >expect &&
+                       git rev-parse HEAD >actual &&
+
+                       test_cmp expect actual
+               )
+       '
+}
+
+test_reflog_updateref B git reflog delete --updateref HEAD@{0}
+test_reflog_updateref B git reflog delete --updateref HEAD@{1}
+test_reflog_updateref C git reflog delete --updateref main@{0}
+test_reflog_updateref B git reflog delete --updateref main@{1}
+test_reflog_updateref B git reflog delete --updateref --rewrite HEAD@{0}
+test_reflog_updateref B git reflog delete --updateref --rewrite HEAD@{1}
+test_reflog_updateref C git reflog delete --updateref --rewrite main@{0}
+test_reflog_updateref B git reflog delete --updateref --rewrite main@{1}
+test_reflog_updateref B test_must_fail git reflog expire  HEAD@{0}
+test_reflog_updateref B test_must_fail git reflog expire  HEAD@{1}
+test_reflog_updateref B test_must_fail git reflog expire  main@{0}
+test_reflog_updateref B test_must_fail git reflog expire  main@{1}
+test_reflog_updateref B test_must_fail git reflog expire --updateref HEAD@{0}
+test_reflog_updateref B test_must_fail git reflog expire --updateref HEAD@{1}
+test_reflog_updateref B test_must_fail git reflog expire --updateref main@{0}
+test_reflog_updateref B test_must_fail git reflog expire --updateref main@{1}
+test_reflog_updateref B test_must_fail git reflog expire --updateref --rewrite HEAD@{0}
+test_reflog_updateref B test_must_fail git reflog expire --updateref --rewrite HEAD@{1}
+test_reflog_updateref B test_must_fail git reflog expire --updateref --rewrite main@{0}
+test_reflog_updateref B test_must_fail git reflog expire --updateref --rewrite main@{1}
+
+test_done