Improve rosdep: 1) Friendlier to beginners, 2) Clarifying rosdep is ROS-agnostic

[130s]

Current rendition is great, then I noticed there might be some more things the beginners and experienced rosdep users like to know.

Issue

• Giving an impression that rosdep is ros-dependent. It is actually widely applicable in non-ROS projects.
  • Not knowing rosdep being non-ros dependent matters IMO where the development involves non-ROS environment e.g. corporate, where people tend to end up inventing their own dependency management framework that runs alongside of rosdep, resulted in rosdep not receiving contribution.
• Trying to make it friendlier to non-expert readers by clarifyig rosdistro website and some jargons.
• Explanation of <*depend> is missing.

Solution approach

• Avoid giving an impression that rosdep is ros-dependent. It is actually widely applicable than ROS projects.
• Trying to make it friendlier to non-expert readers by clarifyig rosdistro website and some jargons.
• Added a link to http://docs.ros.org/en/melodic/api/catkin/html/howto/format2/catkin_library_dependencies.html
  • Thought I'd add those in here but ran out of time. I don't know if rosdep page is the best for such info anyways.

[fujitatomoya]

overall, i am good to take this improvement, probably we can keep this open for more feedback.

[clalancette]

@130s FYI, I spent some time and cleaned this up to be closer to what I think it should look like. What I did was to get rid of the separate "define_dependencies" file, and moved that content into Rosdep.rst. Once that was done, there was no need to move the Rosdep file, so I moved that back to its original location. Then I went through and did a bunch of editing, cleaning things up so most of the information is there but in a different order.

I think I've preserved the essence of what you've done, but please take a look and let me know what you think.

[gavanderhoorn]

Consider adding a why as well. The motivation for rosdep isn't always clear, leading to questions such as why rosdep instead of others? and When should I use rosdep and when should I use apt or pip?

[clalancette]

I've added a couple of sentences about this in fcdc39d . Let me know what you think.

[130s]

@clalancette I "approved" (if there were a button I'd hit it). Thanks for cleaning my PR.

In one of the links @gavanderhoorn referred to, I found that there's yet another good set of documentation about rosdep http://docs.ros.org/en/independent/api/rosdep/html/. It's "independent", which I assume means "not dependent on any ros1 distro", meaning the web location is still under ros1 hence ROS2 maintainers may not want this PR to refer to it. But if linking from this PR to it is not an issue I'd suggest we should link, in a hope we wouldn't duplicate rosdep documentation in the future.

[clalancette]

In one of the links @gavanderhoorn referred to, I found that there's yet another good set of documentation about rosdep http://docs.ros.org/en/independent/api/rosdep/html/. It's "independent", which I assume means "not dependent on any ros1 distro", meaning the web location is still under ros1 hence ROS2 maintainers may not want this PR to refer to it. But if linking from this PR to it is not an issue I'd suggest we should link, in a hope we wouldn't duplicate rosdep documentation in the future.

Yes, good point. That is independent of any ROS distributions, so we can include a link here. I'll find a place to put it.