How to maintain several versions of a ros based robot?

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Managing version across multiple repositories is not easy. I experienced the same issue in my job.

What I would advise is the following. The first step is to isolate those differences, which can be:

• different nodes
• same nodes different params
• same package, different features=different git commit

Next, create a package for each robot (let's say you have 2 robots): robot1_robot & robot2_robot.

Create a common_robot package that will contains launch files, and params common to both robot. Then, each robot package will contain its specific launches & params, you will also include the common_robot launches that are needed.

Those 3 pkgs will only contain params and launches that include node from your other pkgs. Each of these 3 packages is then git-ed and versionned.

Finally, to track the version of robot1 for example, create a workspace for robot1. Clone in the packages robot1 depends on: robot1_robot, common_robot, pkgA, ..., pkgF. Checkout each one of them to the version needed by robot1. You can then either use vcs-tool to export the workspace to a yaml file, you then can update the yaml with every update. Or you can create a git submodule.

It's a lot, but don't hesitate if you have questions :)

The most flexible answer would be to use different params files. That way you will have different features for 'robot1' and 'robot2' rather easily. The benefit being that when you test or make changes you do not have to build your system each and every-time. You can also make individual packages for each robot but creating folders called 'robot1' and 'robot2' inside the same package will also do the trick. Params as I know have their limitations.

But it also depends on the complexity. If the differences cannot be handled by rosparam then you can also have several working branches in git for each of your individual packages. This way your system would be very modular. Then with git you will have three branches for each package: 'robot1', 'robot2' and 'common' so that if there are packages you want to update for both robots, you can simply upload it to the 'common' branch.

The solution with #define is a bit tricky as it would make a single file very flexible, but this would also make the code structure a bit complex. I would choose this as the last option.