allow linting based on test dependencies only

[dirk-thomas]

• add ament_lint_auto
• add ament_lint_common
• update all linter packages to implement extension point of ament_lint_auto

@esteve @tfoote @wjwwood Please review.

[wjwwood]

What direct is this glob done in? Should these be prefixed with CMAKE_CURRENT_SOURCE_DIR?

[dirk-thomas]

Most CMake commands are relative to the CMAKE_CURRENT_SOURCE_DIR if not specified otherwise.

[wjwwood]

I was just imagining someone causing this hook to happen while in a sub-CMakeLists.txt, like one in the test folder. I thought the glob would be relative to the CMAKE_CURRENT_LIST_DIR instead.

[dirk-thomas]

These hook files are only used through ament_lint_auto which itself gets triggered by the ament_package extension point. So this will always be in the root of the package.

[wjwwood]

Ok, sounds good.

[wjwwood]

Other than some questions (and several useless comments...) lgtm. +1

[wjwwood]

All my comments have been addressed +1

[tfoote]

lgtm

[esteve]

+1

[dirk-thomas]

Currently the CMake linter functions have at least one required arguments: the target name.

Should we consider to make it optional?

• pro: usually each function is only called once, therefore the target name would consistent
• con: when the user calls it twice it results in an error telling the user that he needs to pass a custom target name when calling the function multiple times

[wjwwood]

I think it is ok to make it optional. Users will most likely not call it multiple time and if they do it is easy enough to catch and tell them how to fix the problem. We should, however, make sure to not just let the target name collide but instead detect it and provide a useful warning.