version: use OSS repo's version when building.

When building with redo, also include the git commit hash
from the proprietary repo, so that we have a precise commit
that identifies all build info (including Go toolchain version).

Add a top-level build script demonstrating to downstream distros
how to burn the right information into builds.

Adjust `tailscale version` to print commit hashes when available.

Fixes #841.

Signed-off-by: David Anderson <danderson@tailscale.com>

ipn/local.go

@@ -671,7 +671,7 @@ func (b *LocalBackend) send(n Notify) {
 	b.mu.Unlock()
 
 	if notify != nil {
-		n.Version = version.LONG
+		n.Version = version.Long
 		notify(n)
 	} else {
 		b.logf("nil notify callback; dropping %+v", n)
@@ -945,7 +945,7 @@ func (b *LocalBackend) parseWgStatus(s *wgengine.Status) (ret EngineStatus) {
 		// [GRINDER STATS LINE] - please don't remove (used for log parsing)
 		b.keyLogf("peer keys: %s", strings.Join(peerKeys, " "))
 		// [GRINDER STATS LINE] - please don't remove (used for log parsing)
-		b.logf("v%v peers: %v", version.LONG, strings.Join(peerStats, " "))
+		b.logf("v%v peers: %v", version.Long, strings.Join(peerStats, " "))
 	}
 	return ret
 }