test_expect_success \
'prepare repository with topic branches' \
- 'echo First > A &&
+ 'git config core.logAllRefUpdates true &&
+ echo First > A &&
git update-index --add A &&
git commit -m "Add A." &&
git checkout -b my-topic-branch &&
GIT_TRACE=1 git rebase master
'
+test_expect_success 'HEAD was detached during rebase' '
+ test $(git rev-parse HEAD@{1}) != $(git rev-parse modechange@{1})
+'
+
+test_expect_success 'Show verbose error when HEAD could not be detached' '
+ : > B &&
+ test_must_fail git rebase topic 2> output.err > output.out &&
+ grep "Untracked working tree file .B. would be overwritten" output.err
+'
+
test_done