Add replacement rule for gazebo11 (classic) to allow overwriting of gz CLI executable

[methylDragon]

Part of: gazebo-tooling/release-tools#698

This install rule targets gazebo.install file for gazebo11, which installs the gz executable. Using the overwriting rules.

I am unsure if we should have a corresponding line on gazebo11-release to allow Gazebo Classic to be installed on top of the pre-existing (garden) gz executable (overwriting the gz executable then.)

[chapulina]

Ideally we'd remove the breakage of ignition-tools, that was done just so we could iterate faster while both were still installing ign.

My initial inclination would be to:

1. User tries to install gz-tools2
2. If ignition-tools is installed, don't install the ign symlink to gz
3. If ignition-tools isn't installed, install the symlink - but then if the user tries to install ignition-tools afterwards, it would be nice to remove that symlink and let the user know

[methylDragon]

Hmmm, I think it'll need a companion set of PRs for ignition-tools and the corresponding release repo

There are some small complications:

• The flow for deb install is:
  • CMake install() -> file gets put into the CMake install space -> deb packaging takes the install space file and packages it into the debian file according to the .install rules
• As I understand it, debian package management control gives us the tools to specify that it's ok to overwrite files, but not to fail gracefully if files aren't installed on the CMake side.
  • i.e. Files MUST be installed on the CMake side in order to be packaged in the deb. If they're not and they're specified for inclusion, things break (I guess unless we use a regex match somehow..?)

I think there's a way to achieve what we want, but it'll be a bit janky.

Flow

User tries to install gz-tools2

If ignition-tools is installed, don't install the ign symlink to gz

• If we don't install() the symlink, we can't put the install directive into the debian package using .install, causing an error.
• So most likely what I will do, is try to copy paste the ignition-tools ign executable to the ignition-tools2 CMake install space and package that (instead of creating, installing, and packaging the symlink when ignition-tools_FOUND)

If ignition-tools isn't installed, install the symlink

• This is fine

but then if the user tries to install ignition-tools afterwards, it would be nice to remove that symlink and let the user know

• This will be achieved by installing the symlink in the ignition-tools2 install space, and overwriting the pre-existing one as specified in the debian control file

Control File Reqs

This will need:

• Breaks and Replaces directives on control to allow overwriting files for:
  • on ignition-tools: ignition-tools2
  • on ignition-tools2: ignition-tools

[chapulina]

Thanks for documenting all this, let's go with the current implementation for now and revisit later.