git-show: do not segfault when showing a bad tag

When a tag points at a bad or nonexistent object, we should diagnose the
breakage and exit.  An earlier commit 4f3dcc2 (Fix 'git show' on signed
tag of signed tag of commit, 2008-07-01) lost this check and made it
segfault instead; not good.

This fixes it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin-log.c b/builtin-log.c
index 2efe5937346ee7c0a4d85e4087a4ea49a9806005..db71e0da745ee480f8705c81f2899daf1dc6c4f5 100644 (file)
--- a/builtin-log.c
+++ b/builtin-log.c
@@ -356,7 +356,13 @@ int cmd_show(int argc, const char **argv, const char *prefix)
                                        t->tag,
                                        diff_get_color_opt(&rev.diffopt, DIFF_RESET));
                        ret = show_object(o->sha1, 1, &rev);
-                       objects[i].item = parse_object(t->tagged->sha1);
+                       if (ret)
+                               break;
+                       o = parse_object(t->tagged->sha1);
+                       if (!o)
+                               ret = error("Could not read object %s",
+                                           sha1_to_hex(t->tagged->sha1));
+                       objects[i].item = o;
                        i--;
                        break;
                }

diff --git a/t/t7007-show.sh b/t/t7007-show.sh
new file mode 100755 (executable)
index 0000000..cce222f
--- /dev/null
+++ b/t/t7007-show.sh
@@ -0,0 +1,20 @@
+#!/bin/sh
+
+test_description='git show'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+       echo hello world >foo &&
+       H=$(git hash-object -w foo) &&
+       git tag -a foo-tag -m "Tags $H" $H &&
+       HH=$(expr "$H" : "\(..\)") &&
+       H38=$(expr "$H" : "..\(.*\)") &&
+       rm -f .git/objects/$HH/$H38
+'
+
+test_expect_success 'showing a tag that point at a missing object' '
+       test_must_fail git --no-pager show foo-tag
+'
+
+test_done