Add 'src action create' cmd to create empty action definition (#172)

* Add 'src action create' cmd to create empty action definition

This fixes #153 but depends on #171.

* Allow $schema property in Action Definition

Author: mrnugget

cmd/src/actions_create.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"os"
+)
+
+const actionDefinitionTemplate = `{
+  "$schema": "https://github.com/sourcegraph/src-cli/tree/master/schema/actions.schema.json",
+  "scopeQuery": "",
+  "steps": [
+  ]
+}
+`
+
+func init() {
+	usage := `
+Create an empty action definition in action.json (if not -o flag is given). This command is meant to help with creating action definitions to be used with 'src actions exec'.
+
+Examples:
+
+  Create a new action definition in action.json:
+
+		$ src actions create
+
+  Create a new action definition in ~/Documents/my-action.json:
+
+		$ src actions create -o ~/Documents/my-action.json
+`
+
+	flagSet := flag.NewFlagSet("create", flag.ExitOnError)
+	usageFunc := func() {
+		fmt.Fprintf(flag.CommandLine.Output(), "Usage of 'src actions %s':\n", flagSet.Name())
+		flagSet.PrintDefaults()
+		fmt.Println(usage)
+	}
+
+	var (
+		fileFlag = flagSet.String("o", "action.json", "The destination file name. Default value is 'action.json'")
+	)
+
+	handler := func(args []string) error {
+		flagSet.Parse(args)
+
+		if _, err := os.Stat(*fileFlag); !os.IsNotExist(err) {
+			return fmt.Errorf("file %q already exists", *fileFlag)
+		}
+
+		return ioutil.WriteFile(*fileFlag, []byte(actionDefinitionTemplate), 0644)
+	}
+
+	// Register the command.
+	actionsCommands = append(actionsCommands, &command{
+		flagSet:   flagSet,
+		handler:   handler,
+		usageFunc: usageFunc,
+	})
+}

schema/actions.schema.json

@@ -11,6 +11,11 @@
     "steps"
   ],
   "properties": {
+    "$schema": {
+      "description": "URL of the JSON Schema for an Action Definition.",
+      "type": "string",
+      "minLength": 1
+    },
     "scopeQuery": {
       "description": "A Sourcegraph search query to generate a list of repositories over which to run the action. Use 'src actions scope-query' to see which repositories are matched by the query.",
       "type": "string",