This rewrite:
* Fixes some shellcheck issues (bad quoting, use of | instead of ||
near the beginning of the file)
* Automatically computes the version prefix, depend directory, etc.,
and provides instructions to override this with env vars if the
user really wants to do this.
* Detects when it would be destructive and refuses to run unless
passed the -f flag, rather than prompting the user for a yes/no
* Adds the capability to use cp rather than git clone, which I need
to run this from within Nix.
* Whitelists CHANGELOG.md which shouldn't get substituted.
Andrew Poelstra
Steven Roose