When executing with bundle exec rake parallel:spec and specifying a folder, unnecessary specs also get executed.

[yokei-dev]

Hello！

Summary

When executing with bundle exec rake parallel:spec and specifying a folder, unnecessary specs also get executed.

Steps to Reproduce

Conditions

We have our specs in a file structure that looks like this.
We want execute spec files only in target_folder.

project_root/
    spec/
        non_target_spec.rb
    target_folder/
        spec/
            target_spec.rb

Executed command

bundle exec rake parallel:spec['spec','-- target_folder']

Expected Behavior

spec files only in target_folder are executed

Actual Behavior

spec files are executed, including non_target_spec.rb

My opinion

I understand this problem can avoid by using other command.
That's it #434
bundle exec parallel_rspec target_folder

I'm considering making changes because unnecessary operations might be causing this issue.
https://github.com/grosser/parallel_tests/blob/master/lib/parallel_tests/tasks.rb#L120
I want suggest like this.

diff --git a/lib/parallel_tests/tasks.rb b/lib/parallel_tests/tasks.rb
index efda5cd..a22fcfb 100644
--- a/lib/parallel_tests/tasks.rb
+++ b/lib/parallel_tests/tasks.rb
@@ -117,7 +117,7 @@ module ParallelTests
         executable = ParallelTests.with_ruby_binary(executable)
 
-        command = [*executable, type, '--type', test_framework]
+        command = [*executable, '--type', test_framework]
         command += ['-n', count.to_s] if count

I track the process when executed bundle exec rake parallel:spec['spec','-- target_folder'].

In this case, the type variable contains the string value "spec".
It hasn't been specified with options like -n or -p, so when executing OptionParse, "spec" strings remain in the args.
https://github.com/grosser/parallel_tests/blob/master/lib/parallel_tests/cli.rb#L288
and then, in extract_file_paths(argv) method, "spec" is returned unintentionally with "target_folder".
As a result, spec files are executed, including non_target_spec.rb

So, I think type is unnessesary in https://github.com/grosser/parallel_tests/blob/master/lib/parallel_tests/tasks.rb#L120
Even if folder is not specified, spec folder is specified by default_test_folder method. so, i think no problem. https://github.com/grosser/parallel_tests/blob/master/lib/parallel_tests/cli.rb#L300

Please let me know if you have any concerns regarding this change.
If there are no concerns, I'll go ahead and submit a PR!

This is my first time submitting an issue, so I apologize if I said anything odd or out of place.

[grosser]

The first argument is not the type but a regex to find files, from readme:

rake parallel:test[user]  # run users_controller + user_helper + user tests

so putting spec there makes it find all files with spec in the name
just don't do that ?

bundle exec rake parallel:spec['target_folder/']