[PATCH 1/2] t/t1417: test symbolic-ref effects on ref logs

["Kyle J. McKay" <mackyle@gmail.com>]

The git command `git symbolic-ref <refname1> <refname2>` updates
<refname1> to be a "symbolic" pointer to <refname2>.  No matter
what future value <refname2> takes on, <refname1> will continue
to refer to that future value since it's "symbolic".

Since commit 523fa69c36744ae6 ("reflog: cleanse messages in the refs.c
layer", 2020-07-10, v2.29.0), the effect of using the aforementioned
"symbolic-ref" command on ref logs has changed in an unexpected way.

Add a new set of tests to exercise and demonstrate this change
in preparation for correcting it (at which point the failing tests
will be flipped from `test_expect_failure` to `test_expect_success`).

The new test file can be used unchanged to examine this behavior
in much older Git versions (likely to as far back as v2.6.0).

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>
---
 t/t1417-reflog-symref.sh | 91 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100755 t/t1417-reflog-symref.sh

diff --git a/t/t1417-reflog-symref.sh b/t/t1417-reflog-symref.sh
new file mode 100755
index 00000000..6149531f
--- /dev/null
+++ b/t/t1417-reflog-symref.sh
@@ -0,0 +1,91 @@
+#!/bin/sh
+#
+# Copyright (c) 2021 Kyle J. McKay
+#
+
+test_description='Test symbolic-ref effects on reflogs'
+GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	test_commit 'initial' &&
+	git checkout -b unu &&
+	test_commit 'one' &&
+	git checkout -b du &&
+	test_commit 'two' &&
+	git checkout -b tri &&
+	test_commit 'three' &&
+	git checkout du &&
+	test_commit 'twofour' &&
+	git checkout -b KVAR du &&
+	test_commit 'four' &&
+	unu="$(git rev-parse --verify unu)" &&
+	du="$(git rev-parse --verify du)" &&
+	tri="$(git rev-parse --verify tri)" &&
+	kvar="$(git rev-parse --verify KVAR)" &&
+	test -n "$unu" &&
+	test -n "$du" &&
+	test -n "$tri" &&
+	test -n "$kvar" &&
+	test "$unu" != "$du" &&
+	test "$unu" != "$tri" &&
+	test "$unu" != "$kvar" &&
+	test "$du" != "$tri" &&
+	test "$du" != "$kvar" &&
+	test "$tri" != "$kvar" &&
+	git symbolic-ref refs/heads/KVAR refs/heads/du &&
+	kvarsym="$(git rev-parse --verify KVAR)" &&
+	test "$kvarsym" = "$du" &&
+	test "$kvarsym" != "$kvar" &&
+	git reflog exists HEAD &&
+	git reflog exists refs/heads/KVAR &&
+	git symbolic-ref HEAD >/dev/null &&
+	git symbolic-ref refs/heads/KVAR &&
+	git checkout unu &&
+	hcnt=$(git reflog show HEAD | wc -l) &&
+	kcnt=$(git reflog show refs/heads/KVAR | wc -l) &&
+	test -n "$hcnt" &&
+	test -n "$kcnt" &&
+	test $hcnt -gt 1 &&
+	test $kcnt -gt 1 &&
+	test $hcnt -ne $kcnt
+'
+
+test_expect_failure 'HEAD reflog symbolic-ref' '
+	hcnt1=$(git reflog show HEAD | wc -l) &&
+	git symbolic-ref HEAD refs/heads/unu &&
+	git symbolic-ref HEAD refs/heads/du &&
+	git symbolic-ref HEAD refs/heads/tri &&
+	hcnt2=$(git reflog show HEAD | wc -l) &&
+	test $hcnt1 = $hcnt2
+'
+
+test_expect_failure 'refs/heads/KVAR reflog symbolic-ref' '
+	kcnt1=$(git reflog show refs/heads/KVAR | wc -l) &&
+	git symbolic-ref refs/heads/KVAR refs/heads/tri &&
+	git symbolic-ref refs/heads/KVAR refs/heads/du &&
+	git symbolic-ref refs/heads/KVAR refs/heads/unu &&
+	kcnt2=$(git reflog show refs/heads/KVAR | wc -l) &&
+	test $kcnt1 = $kcnt2
+'
+
+test_expect_failure 'double symref reflog symbolic-ref' '
+	hcnt1=$(git reflog show HEAD | wc -l) &&
+	kcnt1=$(git reflog show refs/heads/KVAR | wc -l) &&
+	git symbolic-ref HEAD refs/heads/KVAR &&
+	git symbolic-ref refs/heads/KVAR refs/heads/du &&
+	git symbolic-ref refs/heads/KVAR refs/heads/unu &&
+	git symbolic-ref refs/heads/KVAR refs/heads/tri &&
+	git symbolic-ref HEAD refs/heads/du &&
+	git symbolic-ref HEAD refs/heads/tri &&
+	git symbolic-ref HEAD refs/heads/unu &&
+	hcnt2=$(git reflog show HEAD | wc -l) &&
+	kcnt2=$(git reflog show refs/heads/KVAR | wc -l) &&
+	test $hcnt1 = $hcnt2 &&
+	test $kcnt1 = $kcnt2 &&
+	test $hcnt2 != $kcnt2
+'
+
+test_done
--