Bash completion for flags

[mabelzhang]

🎉 New feature

Part of gazebosim/gz-tools#1
Used together with gazebosim/gz-tools#87

Summary

Bash completion, installation, tests.

Small corner cutting for easier forward-porting:
ign service has --help-all in Fortress+
ign topic has --json-output in Fortress+
This PR targets Citadel, but I've removed those so that the tests don't fail when this is forward-ported to Fortress 😅 We could add a PR to add these back to Citadel - they'd need to be added to both the bash script and the tests. They don't seem like critical flags to be in tab completion, and if a user types --help, they can still see them.

Alternatively, I can add the Citadel-specific flags in this PR, and add a comment to remove them in Fortress?
Update: For correctness, I've gone ahead and do that in 7ccc7a6.

Test it

This works with the installation method in the gz-tools PR described in this comment gazebosim/gz-tools#87 (comment) .

$ . install/share/gz/gz.completion

$ ign service -<tab>
--force-version  --req            --versions       -s
--help           --reqtype        -h               -v
--info           --service        -i               
--list           --timeout        -l               
--reptype        --version        -r               

$ ign topic -<tab>
--duration       --msgtype        -d               -n
--echo           --num            -e               -p
--force-version  --pub            -h               -t
--help           --topic          -i               -v
--info           --version        -l               
--list           --versions       -m            

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

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[mabelzhang]

Just realized there's also the log command. That's a bit different from the rest, as it has a third level of subcommands, ign log record|playback -<flag>. It needs another level of logic in the bash script, similar to ign-tools/etc/ign.bash_completion.sh.

😅 That logic would go where I say in the comments

because we never have two
    # subcommands in the same line. If that is ever needed, change here to
    # detect subsequent subcommands

In the interest of time, I think I will try to cover the two-level flags for as many libraries as possible, for commands like ign <subcommand> -<flag>.

When we have more time, we can come back to the three-level flags, like ign <subcommand> <subsubcommand> -<flag>. So far, I can see that applies to ign log and ign fuel. There may be others.

[chapulina]

Pushed some changes on b6c5430:

• Apply Detect ign instead of using cmake module to check for ignition-tools #249 to this branch, so it's on track with other libs
• Make sure we install CLI files even if ign isn't present
• Fix tests accordingly