Make container env variable conditional

Add only when it's not already present.

Add a more specific version in podman spec generation
so we get 'container=podman' not 'container=libpod'

Signed-off-by: Matthew Heon <matthew.heon@gmail.com>

Closes: #540
Approved by: baude

cmd/podman/spec.go

@@ -195,6 +195,7 @@ func createConfigToOCISpec(config *createConfig) (*spec.Spec, error) {
 	for sysctlKey, sysctlVal := range config.Sysctl {
 		g.AddLinuxSysctl(sysctlKey, sysctlVal)
 	}
+	g.AddProcessEnv("container", "podman")
 
 	// RESOURCES - MEMORY
 	if config.Resources.Memory != 0 {

libpod/container_internal.go

@@ -909,7 +909,18 @@ func (c *Container) generateSpec() (*spec.Spec, error) {
 
 	g.SetHostname(c.Hostname())
 	g.AddProcessEnv("HOSTNAME", g.Spec().Hostname)
-	g.AddProcessEnv("container", "libpod")
+
+	// Only add container environment variable if not already present
+	foundContainerEnv := false
+	for _, env := range g.Spec().Process.Env {
+		if strings.HasPrefix(env, "container=") {
+			foundContainerEnv = true
+			break
+		}
+	}
+	if !foundContainerEnv {
+		g.AddProcessEnv("container", "libpod")
+	}
 
 	return g.Spec(), nil
 }