chore(generator): always use lib name as "generated by"

[matansh]

Problem

In the project I am working on we want to use //go:generate go run github.com/globusdigital/deep-copy [args...] instead of forcing all of our contributors to install deep-copy locally. (I assume we are not the only ones)

When deep-copy is invoked via go run it creates the following comment on the auto generated files

// generated by /tmp/go-build335036942/b001/exe/deep-copy [args...]

This is problematic because:

• Every PR out contributors will raise will contain a different go-buildxxxx which is unneeded noise
• We run go generate ./... in our CI to validate that contributors have not forgotten to update required autogenerated code in their PRs, this CI job will always fail as it will alter the go-buildxxxx

Solution

Normalize the output of the code generator so no-op regeneration results in no diffs.

Notes

• Even in the testing of the lib this problem was encountered, but instead of fixing it the tests were made to ignore the unwanted diff.
• https://github.com/vektra/mockery a popular lib that generates mocks is an example of a code generator that always results in the comment // Code generated by mockery. allowing users to safely invoke it via go run .

[matansh]

@urandom @egawata @romshark I don't know if anyone is actively subscribed to notifications from this repo, there are no reviewers automatically assigned to PRs, and I could not find contribution guidelines so I am using @ as a low tech way to ping the top contributors in order to make sure there is visibility for this proposal. (sorry not sorry :wink: )

[egawata]

@matansh I've created PRs for this repo several times, and @urandom reviewed them. I believe he'll find this PR, so it would be good to wait a few days.