Rather than copying in .proto files, use the same symlink
trick we do for doing the actual etcd build.
Also check for exact version of protoc early on.
Using Go-style import paths in protos is not idiomatic. Normally, this
detail would be internal to etcd, but the path from which gogoproto
is imported affects downstream consumers (e.g. cockroachdb).
In cockroach, we want to avoid including `$GOPATH/src` in our protoc
include path for various reasons. This patch puts etcd on the same
convention, which allows this for cockroach.
More information: https://github.com/cockroachdb/cockroach/pull/2339#discussion_r38663417
This commit also regenerates all the protos, which seem to have
drifted a tiny bit.
