add :before option to run source ~/.bashrc

[sugitak]

About

This pull request adds :before option on Command, which let us run other preparation command beforehand.
Typical usage is to run source ~/.bashrc before running a command.

Problem

When I run Capistrano, I always run into the environment variable problem. I just want to read ~/.bashrc to set my $PATH, but I have to set it in my config/deploy.rb.

Adding environments variable is not always a good way. Situations I have experienced is:

• Ruby is installed via rbenv, which means I can't run bundle exec rake unless I read ~/.bash_profile
• Environment variables includes confidential information, so they should only be in the production servers, not in deployment codes or in deploy server

Usage

Example from the test:

irb(main):001:0> puts Command.new(:touch, 'somefile', user: 'bob', env: {a: 'b'}, in: '/var', before: 'source ~/.bashrc').to_command
cd /var && umask 007 && ( export A="b" ; sudo -u bob A="b" -- sh -c 'source ~/.bashrc ; /usr/bin/env touch somefile'

[sugitak]

Used in pratical situation, there seems to be some problems left... sorry. I should be fixing the problems.

• prerun commands takes the default_env, and the main command can't receive the env
• want to set default_prerun, but running prerun commands before every command may break the behavior

[leehambley]

Would this be better solved with the more general solution I proposed in #280 ?

[leehambley]

@sugitak you didn't respond to my query 6 months ago about whether the proposed solution in #280 was viable, please report back, and/or close this issue.