context: adding append/remove args option

[jbohren]

• calling catkin config [--append-args | -a] [ARGS] will append elements to list args
• calling catkin config [--remove-args | -r] [ARGS] will remove elements from list args
• also fixing context load/save code style build: making it so ephemeral list-type arguments are appended to existing list-type arguments #147 (comment)
• also fixing line-too-long code style

Fixes #176

[wjwwood]

Should it be (is it?) mentioned somewhere that the default behavior is to replace the list?

[jbohren]

Yeah, that should be made more clear.

[wjwwood]

Other than the comment +1

[hgaiser]

As mentioned in #152 , I think it would be better to let the default behaviour be to add items to a list and have a --clear-[something] to clear the list. This maintains the same functionality with one less argument (and to be honest, is what I would expect it to do).

[jbohren]

As mentioned in #152 , I think it would be better to let the default behaviour be to add items to a list and have a --clear-[something] to clear the list. This maintains the same functionality with one less argument (and to be honest, is what I would expect it to do).

I agree. The -clear-*list arguments were misleading. They've been renamed to --no-whitelist and --no-blacklist so that they conform to the pattern used by other arguments like --cmake-args / --no-cmake-args.

With respect to making it append by default, making the --whitelist and --blacklist options behave differently from --cmake-args and --make-args can make the interface start getting really confusing. I think adding an extra -a to append isn't that onerous.

The real problem here is that "whitelist" can be a noun or a verb. The argument is meant to be a noun, i.e. you're setting the whitelist but it's equally reasonable at first glance to read it as if you're whitelisting a package. I also tried to clarify this in the documentation: https://github.com/catkin/catkin_tools/blame/master/docs/verbs/catkin_config.rst#L239-252

[jbohren]

@wjwwood I've updated the documentation

[wjwwood]

lgtm, thanks.