Added support for the expand option for Issues

The ```expand``` option is used to specify resource expansion in the
Jira REST API.

It's particularly useful for things like fetching the ```changelog``` of
an Issue.

This PR adds the support to the ```ListIssues``` and ```ViewIssue```
functions of the ```jira.Cli``` struct.

I'm happy to add tests, but there is currently no test suite in the
master branch, so I did not want to bog down the PR with tangential features.

cli.go

@@ -21,7 +21,7 @@ import (
 )
 
 var (
-	log     = logging.MustGetLogger("jira")
+	log = logging.MustGetLogger("jira")
 	VERSION string
 )
 
@@ -402,6 +402,10 @@ func (c *Cli) SaveData(data interface{}) error {
 
 func (c *Cli) ViewIssue(issue string) (interface{}, error) {
 	uri := fmt.Sprintf("%s/rest/api/2/issue/%s", c.endpoint, issue)
+	if x := c.expansions(); len(x) > 0 {
+		uri = fmt.Sprintf("%s?expand=%s", uri, strings.Join(x, ","))
+	}
+
 	data, err := responseToJson(c.get(uri))
 	if err != nil {
 		return nil, err
@@ -463,6 +467,7 @@ func (c *Cli) FindIssues() (interface{}, error) {
 		"startAt":    "0",
 		"maxResults": c.opts["max_results"],
 		"fields":     fields,
+		"expand":     c.expansions(),
 	})
 	if err != nil {
 		return nil, err
@@ -499,3 +504,12 @@ func (c *Cli) getOptBool(optName string, dflt bool) bool {
 		return dflt
 	}
 }
+
+// expansions returns a comma-separated list of values for field expansion
+func (c *Cli) expansions() []string {
+	expansions := make([]string, 0)
+	if x, ok := c.opts["expand"].(string); ok {
+		expansions = strings.Split(x, ",")
+	}
+	return expansions
+}

main/main.go

@@ -203,6 +203,7 @@ Command Options:
 		"remove":                setopt,
 		"r|reporter=s":          setopt,
 		"f|queryfields=s":       setopt,
+		"x|expand=s":            setopt,
 		"s|sort=s":              setopt,
 		"l|limit|max_results=i": setopt,
 		"o|override=s%":         &opts,