Updated docs for openshift buildconfig feature

- Added buildconfig doc in user guide.
- Add inline code documentation to explain why buildconfig
  object needs to be created after imagestream, because of
  https://github.com/openshift/origin/issues/4518

docs/user-guide.md

@@ -95,7 +95,7 @@ INFO[0000] file "result-imagestream.json" created
 ```
 
 In similar way you can convert DAB files to OpenShift.
-```console$
+```console
 $ kompose --bundle docker-compose-bundle.dab --provider openshift convert
 WARN[0000]: Unsupported key networks - ignoring
 INFO[0000] file "redis-svc.json" created
@@ -106,6 +106,19 @@ INFO[0000] file "redis-deploymentconfig.json" created
 INFO[0000] file "redis-imagestream.json" created
 ```
 
+It also supports creating buildconfig for build directive in a service. By default, it uses the remote repo for the current git branch as the source repo, and the current branch as the source branch for the build. You can specify a different source repo and branch using ``--build-repo`` and ``--build-branch`` options respectively.
+
+```console
+kompose --provider openshift --file buildconfig/docker-compose.yml convert
+WARN[0000] [foo] Service cannot be created because of missing port. 
+INFO[0000] Buildconfig using git@github.com:rtnpro/kompose.git::master as source. 
+INFO[0000] file "foo-deploymentconfig.json" created     
+INFO[0000] file "foo-imagestream.json" created          
+INFO[0000] file "foo-buildconfig.json" created 
+```
+
+**Note**: If you are manually pushing the Openshift artifacts using ``oc create -f``, you need to ensure that you push the imagestream artifact before the buildconfig artifact, to workaround this Openshift issue: https://github.com/openshift/origin/issues/4518 .
+
 ## Kompose up
 
 Kompose supports a straightforward way to deploy your "composed" application to Kubernetes or OpenShift via `kompose up`.
@@ -354,4 +367,4 @@ services:
   mariadb:
     image: centos/mariadb
     restart: "no"
-```
+```

pkg/transformer/openshift/openshift.go

@@ -329,6 +329,7 @@ func (o *OpenShift) Transform(komposeObject kobject.KomposeObject, opt kobject.C
 				objects = append(objects, o.initImageStream(name, service))
 			}
 
+			// buildconfig needs to be added to objects after imagestream because of this Openshift bug: https://github.com/openshift/origin/issues/4518
 			if service.Build != "" {
 				if !hasBuild {
 					composeFileDir, err = getComposeFileDir(opt.InputFile)