--- Data stack:
"diff --git a/hgext/churn.py b/hgext/churn.py"
R! diff --git a/(.*) b/(.*)!
( scratchpad ) (match) captured-groups>>

--- Data stack:
H{ ~array~ ~array~ }
( scratchpad ) .
H{
    {
        1
        T{ slice
            { from 13 }
            { to 13 }
            { seq
                "diff --git a/hgext/churn.py b/hgext/churn.py"
            }
        }
    }
    {
        2
        T{ slice
            { from 30 }
            { to 30 }
            { seq
                "diff --git a/hgext/churn.py b/hgext/churn.py"
            }
        }
    }
}