fix(mkreleaselog): make robust against running in different working directories

[Stebalien]

1. Cd into the repo root before running go list.
2. Make sure the repo lives in the GOPATH.

fixes #7296 (comment)

[ribasushi]

This works too... though... it requires knowing what GOPATH is. Note that I was using "default GOPATH", when I wrote the patch/did the testing. I assume this is the case for most newcomers to go, post-modules, thus the "just go get it" worked for me:

admin:~/devel/go-ipfs$ env | grep GO
[@ Wed 06:00:36.432]
[$?==1  /    0.010s]

admin:~/devel/go-ipfs$ go env | grep PATH
GOPATH="/Users/admin/go"
[@ Wed 06:00:42.708]
[$?==0  /    0.127s]

[Stebalien]

https://github.com/ipfs/go-ipfs/blob/8e7cead9af8fc0d8886e7b601275e6061a526dd6/bin/mkreleaselog#L5

(go env GOPATH will print out the default if the environment variable is unset)

[ribasushi]

@Stebalien I misphrased. What I meant is that the user needs to know what GOPATH is, and most newcomers to go post-modules do not really understand all that (I still don't... fully).

Thus this is a bit cryptic:
https://github.com/ipfs/go-ipfs/blob/048c1c37b3811c1568f7a6f12ae07d2ba24935ed/bin/mkreleaselog#L167

Ok, it requires this, how do I fix it? :) In any case: this is maint tooling, not that important, just wanted to clarify what I meant.

[Stebalien]

Ah, got it. Yeah, I'm tempted to say "if you're messing with this script, you probably know what GOPATH is".