Fix handling of double dashes (--) in crystal eval command

[kojix2]

This pull request has two fixes to the behavior of the eval command.

1. The eval command will now allow you to pass command line arguments to a program using a single double hyphen.
2. When more than one argument is given, they will be joined with “;” instead of “ ”

1 double dash issue

crystal eval 'puts ARGV' -- meow neigh

Expected behavior

["meow", "neigh"]

Actual behavior

syntax error in eval:1
Error: unexpected token: "meow"

Workaround

By using two double dashes, you can pass arguments to the program as expected.

crystal eval 'puts ARGV' -- -- meow neigh

The reason for this behavior is that the OptionParser stops at “--” by default, and removes “--”. Therefore, you need to use unknown_args to distinguish between arguments that were before “--” and arguments that were after “--”.

In the forum, I received a comment that this is probably not the intended behavior.

2 join arguments with “;” instead of “”.

crystal eval "puts 0" "puts 1"

Expected behavior (for kojix2)

0
1

Actual behavior

syntax error in eval:1
Error: unexpected token: "puts"

Personally, I feel that this behavior is preferable.
In many programming languages, only one argument is accepted.

python3 -c "print(0)" -c "print(1)"

0

In Ruby, multiple arguments are accepted.

ruby -e "puts 0" -e "puts 1"

0
1

However, if the opinion that the current behavior should be maintained for compatibility or other reasons is stronger, I can fully understand that.

---

Also, there are no tests for this pull request. If tests are necessary, please let me know where and what kind of tests should be written.

[straight-shoota]

Could you please split off the argument join into a separate PR? The changes are related in the code they affect, but they're different issues and should be considered independently.
Thanks.

[kojix2]

Thanks. I did it.

[straight-shoota]

FTR, you could've just reverted the second commit in this PR. But creating a new one is fine as well. 👌