Declarative application specifications for Fission (#422)

This change enables users to have declarative specifications for Fission resources. Users can specify their "app" in a set of spec files, and use a new fission CLI command to "apply" these specs to a running cluster.

The new "spec" CLI also includes archiving of local source files, and a file watcher that re-builds archives and uploads them on file changes, and a package build watcher that waits for package builds on the CLI. 

A "--spec" option is also added to "function create", and will be added to other resources in future changes.  This option causes a YAML to be outputted to the specs directory instead of the resource being created on the cluster.

The CLI "fission spec --help" outputs usage information.

fission/function.go

@@ -112,6 +112,14 @@ func fnCreate(c *cli.Context) error {
 		fatal("Need --name argument.")
 	}
 
+	// user wants a spec, create a yaml file with package and function
+	spec := false
+	specFile := ""
+	if c.Bool("spec") {
+		spec = true
+		specFile = fmt.Sprintf("function-%v.yaml", fnName)
+	}
+
 	fnList, err := client.FunctionList()
 	checkErr(err, "get function list")
 	// check function existence before creating package
@@ -182,7 +190,7 @@ func fnCreate(c *cli.Context) error {
 		buildcmd := c.String("buildcmd")
 
 		// create new package
-		pkgMetadata = createPackage(client, envName, srcArchiveName, deployArchiveName, buildcmd)
+		pkgMetadata = createPackage(client, envName, srcArchiveName, deployArchiveName, buildcmd, specFile)
 	}
 
 	//TODO Warn user about resources at fn level overriding the env resources
@@ -241,6 +249,14 @@ func fnCreate(c *cli.Context) error {
 		function.Spec.ConfigMaps = append(function.Spec.ConfigMaps, newCfgMap)
 	}
 
+	// if we're writing a spec, don't create the function
+	if spec {
+		err = specSave(*function, specFile)
+		checkErr(err, "create function spec")
+		return nil
+
+	}
+
 	_, err = client.FunctionCreate(function)
 	checkErr(err, "create function")