Alias hardcoded commands as official test commands

[AlexB52]

When retest is used with custom bin commands like bin/test <test>, retest will default to a hardcoded command that will not support running all tests nor run forced selection of tests or differ branches.

This issue will reuse the options available on retest like --rspec, --rake, --rails and link them to hardcoded command if specified

Example:

$ retest --rspec "bin/test <test>" should follow rspec rules around batching test files or run all the specs like this:

• run all: bin/test
• run multiple: bin/test path1_spec.rb path2_spec.rb
• run one test: bin/test path1_spec.rb

Note, --rails option should work just like --rspec option.

Similarly:

$ retest --rake "bin/test TEST=<test>" should follow rake rules around batching test files or run all the specs like this:

• run all: bin/test
• run multiple: bin/test TEST={path1_spec.rb,path2_spec.rb}
• run one test: bin/test TEST=path1_spec.rb

Finally

$ retest --ruby "bin/test <test>" should follow ruby rules around batching test files or run all the specs like this:

• run all: raise Exception
• run multiple: bin/test -e "require './a/file/path.rb';require './another/file/path.rb';"
• run one test: bin/test a/file/path.rb