tag: advise on nested tags

Robert Dailey reported confusion on the mailing list about a nested
tag which was most likely created by mistake. Jeff King noted that
this isn't a very common case and creating a tag-to-a-tag can be a
user-error.

Suggest that it may be a mistake with an advice message when
creating such a tag.  Those who do want to create a tag that point
at another tag regularly can turn it off with the usual advice
mechanism.

Reported-by: Robert Dailey <rcdailey.lists@gmail.com>
Helped-by: Jeff King <peff@peff.net>
Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Denton Liu <liu.denton@gmail.com>
[jc: fixed test style and tweaked the log message]
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/advice.h b/advice.h
index f875f8cd8d..cb5d361614 100644
--- a/advice.h
+++ b/advice.h
@@ -26,6 +26,7 @@ extern int advice_ignored_hook;
 extern int advice_waiting_for_editor;
 extern int advice_graft_file_deprecated;
 extern int advice_checkout_ambiguous_remote_branch_name;
+extern int advice_nested_tag;
 
 int git_default_advice_config(const char *var, const char *value);
 __attribute__((format (printf, 1, 2)))