If we look at the shards --help output, it says that we can pas <options> to the build argument:

build [<targets>] [<options>]  - Build the specified <targets> in `bin` path.

The options (that are defined in the same help output) are:

Options:
    --no-color                       Disable colored output.
    --version                        Print the `shards` version.
    --production                     Run in release mode. No development dependencies and strict sync between shard.yml and shard.lock.
    --local                          Don't update remote repositories, use the local cache only.
    -v, --verbose                    Increase the log verbosity, printing all debug statements.
    -q, --quiet                      Decrease the log verbosity, printing only warnings and errors.
    -h, --help                       Print usage synopsis.

It doesn't say that the build options aren't the ones that are specified in the shards --help output, so I assumed (and I'm sure many would fall in the same hole) that shard build --production would get me a release ready binary file, but it doesn't, because the correct option for that is --release and --production is never actually passed to crystal build internally.

So, my suggestions are either:

1. Explicitly specify that the <options> in the build arg belong to crystal build options and not to shards options.
   or
2. Pass --production arg to crystal build arguments (but of course, as --release).
   or
3. Remove the ability to build source code thru shards (since it's just a dep manager) and advise to always use crystal build instead