Add --debug build flag to include Delve debugger

[creydr]

Currently the entrypoint of the image is always set to /ko-app/<app-name>. This makes it hard to remote debug the app via Delve, which invokes the app e.g. via dlv exec <path-to-app>).

This PR adds a new build flag (--debug), which adds the Delve debugger to the image and sets the entrypoint to invoke delve instead of the ko-app directly.

Hint:

• This idea came out of Introduce --disable-entrypoint-overwrite option to allow to disable entrypoint overwrite #1138 (comment).
• I have only tested it on Linux. Tests on MacOS & Windows are welcome :)
• To allow a more customized exec configuration of delve (e.g. specify port, etc.), we could allow more configuration flags, to override the default delve args. But I would see this as a follow up, to not blow up this initial PR. (IMO)

How to test this PR:

1. Apply a manifests with the debug flag. e.g. ko apply --debug -f config/controller.yaml
2. Start a port forwarding for Delve: kubectl port-forward deploy/my-controller 40000:40000
3. Connect from your IDE to the remote debugger. E.g. use the following VSCode launch config:

   {
       "version": "0.2.0",
       "configurations": [{
               "name": "Attach to remote",
               "type": "go",
               "request": "attach",
               "mode": "remote",
               "port": 40000,
               "host": "0.0.0.0",
               "showLog": true,
               "cwd": "${workspaceFolder}"
           }
       ]
   }
   

[creydr]

Hi @imjasonh,
regarding the discussion in #1138, I came up now with the --debug option as an alternative (and from a user perspective simpler) approach.

[creydr]

Hi @imjasonh,
could you check on this PR?

[codecov-commenter]

Codecov Report

Attention: 36 lines in your changes are missing coverage. Please review.

Comparison is base (cf3e626) 49.34% compared to head (15f5078) 49.87%.
Report is 20 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1148      +/-   ##
==========================================
+ Coverage   49.34%   49.87%   +0.53%     
==========================================
  Files          44       44              
  Lines        3640     3743     +103     
==========================================
+ Hits         1796     1867      +71     
- Misses       1614     1637      +23     
- Partials      230      239       +9     

Files	Coverage Δ
pkg/build/options.go	66.66% <100.00%> (+1.96%)	⬆️
pkg/commands/options/build.go	68.80% <100.00%> (+0.50%)	⬆️
pkg/commands/resolver.go	36.01% <0.00%> (-0.44%)	⬇️
pkg/build/gobuild.go	58.48% <65.95%> (+1.17%)	⬆️

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[creydr]

Hello @jonjohnsonjr,
I saw your name in the MAINTAINERS.md file :) Could you check on this PR or help me to find someone who can review it?
Thanks a lot in advance

[creydr]

Friendly reminder about this 😁

[cpanato]

sounds good, but I am not sure if we want to install this tool without any checks,

but i will defer to @imjasonh

[creydr]

Rebased to solve merge conflicts.
@imjasonh is there a way you find some time to check on this? Or any other advice how we can proceed here? If you don't want such functionality in ko, I have to accept it but it would be good for me to know if we can follow up here or if I have to find another way.
Thanks in advance already

[github-actions]

This Pull Request is stale because it has been open for 90 days with
no activity. It will automatically close after 30 more days of
inactivity. Keep fresh with the 'lifecycle/frozen' label.

[github-actions]

This Pull Request is stale because it has been open for 90 days with
no activity. It will automatically close after 30 more days of
inactivity. Keep fresh with the 'lifecycle/frozen' label.

[luhring]

This looks so cool!!!!! I see that conflicts have emerged over time, and I opened #1320 to see if we can get this across the finish line 🏁

[creydr]

This looks so cool!!!!! I see that conflicts have emerged over time, and I opened #1320 to see if we can get this across the finish line 🏁

Hey @luhring,
thanks for checking on this. I rebased it a few days ago, but didn't see any merge conflicts on this (now they probably came via 2a4c12f). Thanks for addressing them already in #1320

[imjasonh]

This is merged! 🎉

Thank you for your patience, and happy debugging! 🐛