Nancy

This release tweaks file copying (of untemplated files) to stop copying the metadata of the files. This means that the files will be copied with a fresh timestamp and default permissions, for example.

This release improves error output when Nancy runs external programs. Standard error from the called program is reprinted, and a more legible error message is given.

This release rejigs Nancy’s command set, in particular how it runs programs. It adds a separate `$run` command, rather than allowing `$include` and `$paste` to take external arguments. It also adds `$expand` to allow the output of `$run` to be expanded.

This release changes the way that external programs are invoked to be more flexible. In particular, the invocation of external programs is now orthogonal to the expansion of `$include` fragments.

This release loosens the requirement for input encoding (which was
undocumented) from UTF-8 to “any 8-bit superset of 7-bit ASCII encoded in 8
bits”. In other words, UTF-8, any ISO-8559-1 encoding, or indeed plain 8-bit
ASCII.

This release fixes a bug where Nancy reported an error when a nested expansion tried to use the same executable via `$include` more than once at different levels. This check is intended to catch infinite expansion of the same non-executable file, and should not be used for executables.