[PATCHv2] checkout: do not mention detach advice for explicit --detach option

[Stefan Beller <sbeller@google.com>]

When a user asked for a detached HEAD specifically with `--detach`,
we do not need to give advice on what a detached HEAD state entails as
we can assume they know what they're getting into as they asked for it.

Signed-off-by: Stefan Beller <sbeller@google.com>
---
 
 jrnieder wrote:
 > Examples?
 
 What do you mean by example?
  
 builtin/checkout.c         |  2 +-
 t/t2020-checkout-detach.sh | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 8d852d4..85408b1 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -658,7 +658,7 @@ static void update_refs_for_switch(const struct checkout_opts *opts,
 		update_ref(msg.buf, "HEAD", new->commit->object.oid.hash, NULL,
 			   REF_NODEREF, UPDATE_REFS_DIE_ON_ERR);
 		if (!opts->quiet) {
-			if (old->path && advice_detached_head)
+			if (old->path && advice_detached_head && !opts->force_detach)
 				detach_advice(new->name);
 			describe_detached_head(_("HEAD is now at"), new->commit);
 		}
diff --git a/t/t2020-checkout-detach.sh b/t/t2020-checkout-detach.sh
index 5d68729..941ea49 100755
--- a/t/t2020-checkout-detach.sh
+++ b/t/t2020-checkout-detach.sh
@@ -163,4 +163,17 @@ test_expect_success 'tracking count is accurate after orphan check' '
 	test_i18ncmp expect stdout
 '
 
+test_expect_success 'no advice given for explicit detached head state' '
+	git config advice.detachedHead false &&
+	git checkout child &&
+	git checkout --detach HEAD >expect &&
+	git config advice.detachedHead true &&
+	git checkout child &&
+	git checkout --detach HEAD >actual &&
+	test_cmp expect actual &&
+	git checkout child &&
+	git checkout HEAD >actual &&
+	! test_cmp expect actual
+'
+
 test_done
-- 
2.9.2.730.g46b112d