crit: fix proto imports for library

[snprajwal]

When using CRIT as a library, all proto bindings are imported and statically linked. This PR aims to fix this by moving each proto binding into its own package and importing all of them only for the CLI to use. The library will be refactored to allow the user to pass the struct instead of deducing it using handler.go

Tasks:

• Use Python script to generate bindings
• Add the imports into handler.go
• Refactor CRIT to receive the struct as an argument

[adrianreber]

Couple of ideas which would be nice to have.

Can you introduce a markdown lint runt like https://github.com/checkpoint-restore/checkpointctl/blob/main/.github/workflows/markdown-lint.yml

This would probably also mean to change the existing top-level README.md. Maybe do the introduction of the markdown lint run as a separate PR.

With the introduction of Python code if would be nice to run the Python code also through a linter like flake8. I think the main CRIU repository has some examples how to use flake8.

[snprajwal]

Got it. I've opened a PR for the markdown linter, I'll add a Python linter along with the script in this PR.

[codecov]

Codecov Report

Patch coverage: 46.27% and project coverage change: -0.51 ⚠️

Comparison is base (45baa8a) 48.84% compared to head (c0cfc38) 48.33%.

❗ Current head c0cfc38 differs from pull request most recent head e69417e. Consider uploading reports for the commit e69417e to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #109      +/-   ##
==========================================
- Coverage   48.84%   48.33%   -0.51%     
==========================================
  Files          22       23       +1     
  Lines        2381     2435      +54     
==========================================
+ Hits         1163     1177      +14     
- Misses       1059     1084      +25     
- Partials      159      174      +15     

Impacted Files	Coverage Δ
crit/decode-extra.go	0.00% <0.00%> (ø)
crit/encode-extra.go	0.00% <0.00%> (ø)
crit/encode.go	19.16% <0.00%> (ø)
scripts/magic-gen/magicgen.go	85.00% <ø> (ø)
crit/cli/handler.go	25.00% <25.00%> (ø)
crit/utils.go	36.60% <40.90%> (ø)
test/crit/main.go	61.53% <47.05%> (-4.70%)	⬇️
crit/image.go	49.46% <50.00%> (+1.54%)	⬆️
crit/cli/cli.go	66.49% <58.51%> (ø)
crit/decode.go	27.21% <62.50%> (-1.46%)	⬇️
... and 5 more

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[snprajwal]

Upon importing the library locally with a simple Go file that looks like below:

package main

import ...

func main() {
    critter := crit.New(...)
    fmt.Println(critter)
}

I noted the following numbers:

• The number of vendored files in crit/images dropped from 145 to 52
• The binary size dropped from 7.3M to 7M, shaving off almost 300KB in the process

[adrianreber]

This PR get really big. Can you move the the last three commits to a separate commit. That looks like something we can merge easily and then you can rebase upon that.

[snprajwal]

Since we have improved error handling substantially in this PR, the coverage has gone down slightly (we cannot test the failure cases like failing to open file, failing to write to file, etc.)

[rst0git]

LGTM

[adrianreber]

@snprajwal Can you post the binary size of phaul (in test) before and after this PR?

A hello world in go needs 1.8MB on my system and the phaul binary needs 7.7MB. What size do you see of the phaul test binary after your changes?

[snprajwal]

What size do you see of the phaul test binary after your changes?

@adrianreber The phaul binary currently sits at 7.2M on my system

[rst0git]

What size do you see of the phaul test binary after your changes?

@adrianreber The phaul binary currently sits at 7.2M on my system

The following results show the size of the phaul binary on my system (Fedora 37 with go version 1.20.3).

Build from master branch:

$ make -C test/ phaul-test
$ ls -alh test/phaul/phaul
-rwxr-xr-x. 1 root root 7.3M May 20 09:12 test/phaul/phaul

Build from fix-proto-gen branch:

$ make -C test/ phaul-test
$ ls -alh test/phaul/phaul
-rwxr-xr-x. 1 root root 7.1M May 20 09:16 test/phaul/phaul

[adrianreber]

Thanks. So this change brings small improvements. Good.