Glad it made sense!

So the match is exact between the non %{..} characters. The idea for scope is the context of the commit, in my libraries I use the name of the class as the scope.

For example with the default format string:

    test string: "fix(User): ensure email address is required"
    format:      "%{type}(%{scope}): %{description}"
    [type: "fix", scope: "User", description: "ensure email address is required"]

So any literal characters are matched exactly and anything inside the capturing %{...} is assigned to that variable.

This does fall over in the following case:

    "fix():(User): ensure email address is required"
    "%{type}(%{scope}): %{description}"
    [type: "fix", scope: "):(User", description: "ensure email address is required"]

It is certainly a candidate for improvement in the future.