Allow conditionals in Bitten recipes

[lowjoel@…]

Perhaps allowing the conditional execution of build steps or indeed, step actions would be a useful addition to recipe parsing, especially when one uses Bitten on multiple environments. Using platform-specific conditional commands, e.g if on most Linux shells vs. cmd's if on Windows uses (slightly?) different syntax and may not be completely portable.

[osimons]

See also the onerror="strip" idea of #623. It allows you to define all steps, and if any error is raised for any reason (accident or intention) the step is just skipped and its presence in the build stripped away in any reporting.

[Joel Low <lowjoel@…>]

#623 seems to only deal with error handling. I was thinking of something more flexible:

<if:equals lhs="${someVar}" rhs="someValue">
    <sh:exec file="whatever" args="whatever"/>
</if>

With more expressive syntax for Boolean operators etc. This isn't really important for the immediate release, but probably would be something nice to think about in the longer term.

[Felix Schwarz <felix.schwarz@…>]

Also to me #623 is not the same – for example I'd like to have an attachment uploaded only if this is a release version (which I can test by checking the version number string).

[james.e.harrison@…]

Our use of Bitten involves cross compiling code, and then copying the code to another (different architecture) machine, and executing tests.

This is done with a "reserved" machine, but the ability to have conditionals in recipes would be a great benefit.

[anatoly techtonik <techtonik@…>]

I'd add skipif attribute to the <step> tag. There might be some code for it in #669