feat(dependency): add diff package to common

[dongjiang1989]

Add diff package to common for client-golang, prometheus and alertmanager.

issue: prometheus/client_golang#1490
pr for client-glang: prometheus/client_golang#1499

[SuperQ]

Wait, no, we should not be copy-pasting code like this.

Fixing an EoL package by replacing it with something not EoL is just fine. There's no need to fully remove a dependency.

CC @kakkoyun

[kakkoyun]

Wait, no, we should not be copy-pasting code like this.

Fixing an EoL package by replacing it with something not EoL is just fine. There's no need to fully remove a dependency.

CC @kakkoyun

We did this in client_golang to reduce the external dependencies. And it is small enough and only used int the tests. I never thought it would be needed elsewhere.

That being said, I'd be more than happy to accept prometheus/client_golang#1539.

[SuperQ]

That was incorrectly done in client_golang. The request was to replace the dependency that was abandoned, not reduce it.

[kakkoyun]

That was incorrectly done in client_golang. The request was to replace the dependency that was abandoned, not reduce it.

I'm well aware of the request. We wanted to kill two birds with one stone.

[ArthurSens]

Add diff package to common for client-golang, prometheus and alertmanager.

I'm not sure if I'm missing something, but does prometheus and alertmanager really use this same logic? I'm aware that client_golang uses this for testing, but maybe we could avoid adding it to common if it's only for client_golang.

Now that prometheus/client_golang#1539 was accepted it's even less important to have this here from my point of view 🤔

[SuperQ]

IMO, we don't want to get into the habit of in-lining Go dependencies. This sets a hard to deal with policy long-term. What is the limit for an inline? How do we keep inline code up-to-date?