(command.CommandList
  children: [
    (command.ShAssignment
      pairs: [
        (assign_pair
          lhs: (sh_lhs_expr.Name name:test_description)
          op: assign_op.Equal
          rhs: {(SQ <'filter-branch removal of trees with null sha1'>)}
          spids: [4]
        )
      ]
    )
    (C {<.>} {<'./test-lib.sh'>})
    (C {<test_expect_success>} {(SQ <'setup: base commits'>)} 
      {(SQ <'\n'> <'\ttest_commit one &&\n'> <'\ttest_commit two &&\n'> <'\ttest_commit three\n'>)}
    )
    (C {<test_expect_success>} {(SQ <'setup: a commit with a bogus null sha1 in the tree'>)} 
      {
        (SQ <'\n'> <'\t{\n'> <'\t\tgit ls-tree HEAD &&\n'> 
          <'\t\tprintf "160000 commit $_z40\\\\tbroken\\\\n"\n'> <'\t} >broken-tree &&\n'> <'\techo "add broken entry" >msg &&\n'> <'\n'> 
          <'\ttree=$(git mktree <broken-tree) &&\n'> <'\ttest_tick &&\n'> <'\tcommit=$(git commit-tree $tree -p HEAD <msg) &&\n'> 
          <'\tgit update-ref HEAD "$commit"\n'>
        )
      }
    )
    (C {<test_expect_success>} {(SQ <'setup: bring HEAD and index in sync'>)} 
      {(SQ <'\n'> <'\ttest_tick &&\n'> <'\tgit commit -a -m "back to normal"\n'>)}
    )
    (C {<test_expect_success>} {(SQ <'filter commands are still checked'>)} 
      {
        (SQ <'\n'> <'\ttest_must_fail git filter-branch \\\n'> <'\t\t--force --prune-empty \\\n'> 
          <'\t\t--index-filter "git rm --cached --ignore-unmatch three.t"\n'>
        )
      }
    )
    (C {<test_expect_success>} {(SQ <'removing the broken entry works'>)} 
      {
        (SQ <'\n'> <'\techo three >expect &&\n'> <'\tgit filter-branch \\\n'> 
          <'\t\t--force --prune-empty \\\n'> <'\t\t--index-filter "git rm --cached --ignore-unmatch broken" &&\n'> 
          <'\tgit log -1 --format=%s >actual &&\n'> <'\ttest_cmp expect actual\n'>
        )
      }
    )
    (C {<test_done>})
  ]
)