$ go version
go version devel +5c7748dc9d Mon Aug 10 23:44:58 2020 +0000 linux/amd64
$ go tool link -h 2>&1 | grep -A1 linkmode
set link mode
At least, it could tell me what the modes are, and ideally point me at the docs for what they do.
I realise that the compiler and linker are fairly low level and mostusers shouldn't be looking at go tool link -h, but given that -linkmode=external is somewhat well known and widely used, it's confusing that it's hard to find its definition without looking at the code.
Oh, right. That sounds more helpful, though I had forgotten about go doc cmd/link and go tool link -h doesn't point me towards it.
Perhaps we could keep go tool link -h in sync with go doc cmd/link, at least when it comes to flags. And for everything else that isn't flags, go tool link -h could tell the user to look at go doc cmd/link.