branch: allow a no-op "branch -M <current-branch> HEAD"

diff --git a/t/t2020-checkout-detach.sh b/t/t2020-checkout-detach.sh
index 00421453ba26327b929fa7b5133a3072fce2bb03..068fba4c8e8706aa615d0401da1da47901113156 100755 (executable)
--- a/t/t2020-checkout-detach.sh
+++ b/t/t2020-checkout-detach.sh
@@ -11,6 +11,17 @@ check_not_detached () {
        git symbolic-ref -q HEAD >/dev/null
 }
 
+ORPHAN_WARNING='you are leaving .* commit.*behind'
+PREV_HEAD_DESC='Previous HEAD position was'
+check_orphan_warning() {
+       test_i18ngrep "$ORPHAN_WARNING" "$1" &&
+       test_i18ngrep ! "$PREV_HEAD_DESC" "$1"
+}
+check_no_orphan_warning() {
+       test_i18ngrep ! "$ORPHAN_WARNING" "$1" &&
+       test_i18ngrep "$PREV_HEAD_DESC" "$1"
+}
+
 reset () {
        git checkout master &&
        check_not_detached
@@ -19,6 +30,8 @@ reset () {
 test_expect_success 'setup' '
        test_commit one &&
        test_commit two &&
+       test_commit three && git tag -d three &&
+       test_commit four && git tag -d four &&
        git branch branch &&
        git tag tag
 '
@@ -92,4 +105,50 @@ test_expect_success 'checkout --detach moves HEAD' '
        git diff --exit-code two
 '
 
+test_expect_success 'checkout warns on orphan commits' '
+       reset &&
+       git checkout --detach two &&
+       echo content >orphan &&
+       git add orphan &&
+       git commit -a -m orphan &&
+       git checkout master 2>stderr
+'
+
+test_expect_success 'checkout warns on orphan commits: output' '
+       check_orphan_warning stderr
+'
+
+test_expect_success 'checkout does not warn leaving ref tip' '
+       reset &&
+       git checkout --detach two &&
+       git checkout master 2>stderr
+'
+
+test_expect_success 'checkout does not warn leaving ref tip' '
+       check_no_orphan_warning stderr
+'
+
+test_expect_success 'checkout does not warn leaving reachable commit' '
+       reset &&
+       git checkout --detach HEAD^ &&
+       git checkout master 2>stderr
+'
+
+test_expect_success 'checkout does not warn leaving reachable commit' '
+       check_no_orphan_warning stderr
+'
+
+cat >expect <<'EOF'
+Your branch is behind 'master' by 1 commit, and can be fast-forwarded.
+EOF
+test_expect_success 'tracking count is accurate after orphan check' '
+       reset &&
+       git branch child master^ &&
+       git config branch.child.remote . &&
+       git config branch.child.merge refs/heads/master &&
+       git checkout child^ &&
+       git checkout child >stdout &&
+       test_cmp expect stdout
+'
+
 test_done