Backport of cli: report server version into release/1.4.x

.changelog/9159.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+server: Add a git `revision` tag to the serf tags gossiped between servers.
+```

command/agent/agent.go

@@ -171,6 +171,7 @@ func convertServerConfig(agentConfig *Config) (*nomad.Config, error) {
 	conf.EnableDebug = agentConfig.EnableDebug
 
 	conf.Build = agentConfig.Version.VersionNumber()
+	conf.Revision = agentConfig.Version.Revision
 	if agentConfig.Region != "" {
 		conf.Region = agentConfig.Region
 	}

nomad/config.go

@@ -128,6 +128,10 @@ type Config struct {
 	// operators track which versions are actively deployed
 	Build string
 
+	// Revision is a string that carries the version.GitCommit of Nomad that
+	// was compiled.
+	Revision string
+
 	// NumSchedulers is the number of scheduler thread that are run.
 	// This can be as many as one per core, or zero to disable this server
 	// from doing any scheduling work.

nomad/server.go

@@ -1517,6 +1517,7 @@ func (s *Server) setupSerf(conf *serf.Config, ch chan serf.Event, path string) (
 	conf.Tags["region"] = s.config.Region
 	conf.Tags["dc"] = s.config.Datacenter
 	conf.Tags["build"] = s.config.Build
+	conf.Tags["revision"] = s.config.Revision
 	conf.Tags["vsn"] = deprecatedAPIMajorVersionStr // for Nomad <= v1.2 compat
 	conf.Tags["raft_vsn"] = fmt.Sprintf("%d", s.config.RaftConfig.ProtocolVersion)
 	conf.Tags["id"] = s.config.NodeID