Cleanup version introspection

* Unify version checking code into version.go
* Make 'version' available as a job in the engine
* Use simplified version checking code when setting user agent for registry client.

server.go

@@ -144,27 +144,6 @@ func (v *simpleVersionInfo) Version() string {
 	return v.version
 }
 
-// versionCheckers() returns version informations of:
-// docker, go, git-commit (of the docker) and the host's kernel.
-//
-// Such information will be used on call to NewRegistry().
-func (srv *Server) versionInfos() []utils.VersionInfo {
-	v := srv.DockerVersion()
-	ret := append(make([]utils.VersionInfo, 0, 4), &simpleVersionInfo{"docker", v.Version})
-
-	if len(v.GoVersion) > 0 {
-		ret = append(ret, &simpleVersionInfo{"go", v.GoVersion})
-	}
-	if len(v.GitCommit) > 0 {
-		ret = append(ret, &simpleVersionInfo{"git-commit", v.GitCommit})
-	}
-	if kernelVersion, err := utils.GetKernelVersion(); err == nil {
-		ret = append(ret, &simpleVersionInfo{"kernel", kernelVersion.String()})
-	}
-
-	return ret
-}
-
 // ContainerKill send signal to the container
 // If no signal is given (sig 0), then Kill with SIGKILL and wait
 // for the container to exit.
@@ -1874,7 +1853,13 @@ func NewServer(eng *engine.Engine, config *DaemonConfig) (*Server, error) {
 func (srv *Server) HTTPRequestFactory(metaHeaders map[string][]string) *utils.HTTPRequestFactory {
 	srv.Lock()
 	defer srv.Unlock()
-	ud := utils.NewHTTPUserAgentDecorator(srv.versionInfos()...)
+	v := dockerVersion()
+	httpVersion := make([]utils.VersionInfo, 0, 4)
+	httpVersion = append(httpVersion, &simpleVersionInfo{"docker", v.Get("Version")})
+	httpVersion = append(httpVersion, &simpleVersionInfo{"go", v.Get("GoVersion")})
+	httpVersion = append(httpVersion, &simpleVersionInfo{"git-commit", v.Get("GitCommit")})
+	httpVersion = append(httpVersion, &simpleVersionInfo{"kernel", v.Get("KernelVersion")})
+	ud := utils.NewHTTPUserAgentDecorator(httpVersion...)
 	md := &utils.HTTPMetaHeadersDecorator{
 		Headers: metaHeaders,
 	}

version.go

@@ -0,0 +1,33 @@
+package docker
+
+import (
+	"github.com/dotcloud/docker/engine"
+	"github.com/dotcloud/docker/utils"
+	"runtime"
+)
+
+func init() {
+	engine.Register("version", jobVersion)
+}
+
+func jobVersion(job *engine.Job) engine.Status {
+	if _, err := dockerVersion().WriteTo(job.Stdout); err != nil {
+		job.Errorf("%s", err)
+		return engine.StatusErr
+	}
+	return engine.StatusOK
+}
+
+// dockerVersion returns detailed version information in the form of a queriable
+// environment.
+func dockerVersion() *engine.Env {
+	v := &engine.Env{}
+	v.Set("Version", VERSION)
+	v.Set("GitCommit", GITCOMMIT)
+	v.Set("GoVersion", runtime.Version())
+	// FIXME:utils.GetKernelVersion should only be needed here
+	if kernelVersion, err := utils.GetKernelVersion(); err == nil {
+		v.Set("KernelVersion", kernelVersion.String())
+	}
+	return v
+}