cmd/go: missing flags in help output for tool

[howardjohn]

Go version

latest

Output of go env in your module/workspace:

N/A

What did you do?

go help tool

What did you see happen?

No mention of -modfile

What did you expect to see?

Available flags are documented. Given the issues around default modfile sharing with the tools and the main project, using alternative mod files is likely to be very common. Documenting the flags available will ensure users do not reach to weird workarounds rather than just do -modfile=tools/go.mod or similar.

[seankhliao]

There are some additional flags:

• -C
• -modcacherw
• -modfile
• -overlay

[gabyhelp]

Related Issues

• x/tools/go/packages: Config.Env doesn't support -modfile #48482
• cmd/go: 'go list' should set the 'GoMod' field to reflect -modfile #36220 (closed)
• x/tools/gopls (and friends): separate -modfile and -mod out of build flags #41826 (closed)
• cmd/go: confusing error message (or incorrect behavior) when using -modfile with go run #51079 (closed)
• x/website: ref/mod: go get is module aware but doesn't support `-mod` flag #60110 (closed)
• cmd/go: -mod flag doesn't work with module-mode go get #44760 (closed)
• cmd/go: fail if the user tries to modify the GOMOD environment variable #51217
• cmd/go/internal/modload: reject the -modfile flag in workspace mode #60033 (closed)

Related Code Changes

• cmd/go: add -modfile flag that sets go.mod file to read/write
• cmd/go: add -modfile and -modcacherw to go tool

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[cagedmantis]

cc @matloob @samthanawalla

[thepudds]

I'll take a crack at this unless someone else would prefer to do it themselves. (I have a couple of related small WIP doc & help CLs for the new go tool feature; I'll likely open up a separate issue for those).