Function materialize 

pub fn materialize(
    source: &Source,
    dest: &Path,
    ssh: Option<&SshConfig>,
    notes: &mut Vec<String>,
) -> Result<(), Fail>

Put the tree at dest, preserving mtimes. Idempotent by construction: both resolvers are incremental refreshes, so a re-dial costs the changed files and nothing else.

dest is fdl’s directory to manage — rsync --delete and git checkout --force both make the tree match the spec, so an edit made there does not survive.