[PATCH v3 2/2] show-branch: fix SEGFAULT when `--current` and `--reflog` together

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

From: Gregory David <gregory.david@p1sec.com>

If run `show-branch` with `--current` and `--reflog` simultaneously, a
SEGFAULT appears.

The bug is that we read over the end of the `reflog_msg` array after
having `append_one_rev()` for the current branch without supplying a
convenient message to it.

It seems that it has been introduced in:
Commit 1aa68d6735 (show-branch: --current includes the current branch.,
2006-01-11)

Signed-off-by: Gregory DAVID <gregory.david@p1sec.com>
Thanks-to: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 builtin/show-branch.c  | 13 +++++++++++++
 t/t3202-show-branch.sh | 43 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+)

diff --git a/builtin/show-branch.c b/builtin/show-branch.c
index 499ef76a508..50c17fb5c31 100644
--- a/builtin/show-branch.c
+++ b/builtin/show-branch.c
@@ -821,6 +821,19 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
 		}
 		if (!has_head) {
 			const char *name = head;
+			struct object_id oid;
+			char *ref;
+			char *msg;
+			timestamp_t ts;
+			int tz;
+
+			if (!dwim_ref(*av, strlen(*av), &oid, &ref, 0))
+				die(_("no such ref %s"), *av);
+			read_ref_at(get_main_ref_store(the_repository), ref,
+				    flags, 0, i, &oid, &msg, &ts, &tz, NULL);
+
+			reflog_msg[ref_name_cnt] = fmt_reflog(msg, ts, tz,
+							      "(%s) (current) %s");
 			skip_prefix(name, "refs/heads/", &name);
 			append_one_rev(name);
 		}
diff --git a/t/t3202-show-branch.sh b/t/t3202-show-branch.sh
index 7a1be73ce87..7f6ffcf8a57 100755
--- a/t/t3202-show-branch.sh
+++ b/t/t3202-show-branch.sh
@@ -161,4 +161,47 @@ test_expect_success 'show branch --reflog=2' '
 	test_cmp actual expect
 '
 
+test_expect_success 'show branch --reflog=2 --current' '
+	sed "s/^>	//" >expect <<-\EOF &&
+	>	! [refs/heads/branch10@{0}] (4 years, 5 months ago) commit: branch10
+	>	 ! [refs/heads/branch10@{1}] (4 years, 5 months ago) commit: branch10
+	>	  * [branch10] (4 years, 5 months ago) (current) branch: Created from initial
+	>	---
+	>	+ * [refs/heads/branch10@{0}] branch10
+	>	++* [refs/heads/branch10@{1}] initial
+	EOF
+	git show-branch --reflog=2 --current >actual &&
+	test_cmp actual expect
+'
+
+test_expect_success 'show branch --current' '
+	sed "s/^>	//" >expect <<-\EOF &&
+	>	! [branch1] branch1
+	>	 ! [branch2] branch2
+	>	  ! [branch3] branch3
+	>	   ! [branch4] branch4
+	>	    ! [branch5] branch5
+	>	     ! [branch6] branch6
+	>	      ! [branch7] branch7
+	>	       ! [branch8] branch8
+	>	        ! [branch9] branch9
+	>	         * [branch10] branch10
+	>	          ! [master] initial
+	>	-----------
+	>	         *  [branch10] branch10
+	>	        +   [branch9] branch9
+	>	       +    [branch8] branch8
+	>	      +     [branch7] branch7
+	>	     +      [branch6] branch6
+	>	    +       [branch5] branch5
+	>	   +        [branch4] branch4
+	>	  +         [branch3] branch3
+	>	 +          [branch2] branch2
+	>	+           [branch1] branch1
+	>	+++++++++*+ [master] initial
+	EOF
+	git show-branch --current >actual &&
+	test_cmp actual expect
+'
+
 test_done
-- 
2.36.0.876.g7efc8a7728c