cmd/go: newlines inconsistently preserved in go.mod rewriting [1.13 backport]

[gopherbot]

@zx2c4 requested issue #33779 to be considered for backport to the next 1.13 minor release.

@gopherbot please backport this to 1.13, because it's a regression from the 1. 12, and it causes dirty files in version control and disturbs other automated systems that don't appreciate stable file contents flopping around.

[gopherbot]

Change https://golang.org/cl/200118 mentions this issue: cmd/go/internal/modfile: remove preceding empty lines when setting require

[gopherbot]

Change https://golang.org/cl/200118 mentions this issue: [release-branch.go1.13] cmd/go/internal/modfile: remove preceding empty lines when setting require

[av86743]

Isn't it in fact ...: removeall blanklines from require section?

[bcmills]

I don't think we should backport this. It may be a regression, but it's cosmetic at best — and as far as I can tell has a simple workaround (namely, don't add newlines in a require block).

CC @jayconrod

[zx2c4]

@bcmills That's fine with me. Feel free to close this (if jay doesn't disagree).

[toothrot]

Closing this issue, as it doesn't seem to meet our bar of "serious problems with no workaround". Please comment if I am mistaken.