t/t3400-rebase.sh: add more tests to help migrating git-rebase.sh to C

These new tests make sure I don't miss any check being performed before
rebase is proceeded (which is well tested by other tests)

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3400-rebase.sh

@@ -41,9 +41,40 @@ test_expect_success \
      git tag topic
 '
 
+test_expect_success 'rebase on dirty worktree' '
+     echo dirty >> A &&
+     test_must_fail git rebase master'
+
+test_expect_success 'rebase on dirty cache' '
+     git add A &&
+     test_must_fail git rebase master'
+
 test_expect_success 'rebase against master' '
+     git reset --hard HEAD &&
      git rebase master'
 
+test_expect_success 'rebase against master twice' '
+     git rebase master 2>err &&
+     grep "Current branch my-topic-branch is up to date" err
+'
+
+test_expect_success 'rebase against master twice with --force' '
+     git rebase --force-rebase master >out &&
+     grep "Current branch my-topic-branch is up to date, rebase forced" out
+'
+
+test_expect_success 'rebase against master twice from another branch' '
+     git checkout my-topic-branch^ &&
+     git rebase master my-topic-branch 2>err &&
+     grep "Current branch my-topic-branch is up to date" err
+'
+
+test_expect_success 'rebase fast-forward to master' '
+     git checkout my-topic-branch^ &&
+     git rebase my-topic-branch 2>err &&
+     grep "Fast-forwarded HEAD to my-topic-branch" err
+'
+
 test_expect_success \
     'the rebase operation should not have destroyed author information' \
     '! (git log | grep "Author:" | grep "<>")'