Compile Hugo on our own, fix extended version and refactoring

Since the extended version is only available for amd64 I have started to
build Hugo on our own in a multi stage Dockerfile. Now we are installing
both binaries, regular hugo and extended hugo, bundled into the Docker
image.

Beside that the download for regular hugo and extended hugo should also
be more solid now.

After that I have also added more aliases for the environment variables.
As mentioned on some GitHub issue we are also installing more required
packages for a downloaded extended Hugo version as this relies on
libc6-compat and libstdc++.

plugin.go

@@ -16,43 +16,53 @@ type (
 	}
 
 	Config struct {
-		BuildDrafts  bool
-		BuildExpired bool
-		BuildFuture  bool
-		CacheDir     string
-		Config       string
-		Content      string
-		Layout       string
-		Output       string
-		Source       string
-		Theme        string
-		Url          string
-		HugoVersion  string
-		HugoExtended bool
-		Validate     bool
+		URL      string
+		Drafts   bool
+		Expired  bool
+		Future   bool
+		Validate bool
+		Cache    string
+		Config   string
+		Content  string
+		Layout   string
+		Output   string
+		Source   string
+		Theme    string
+		Version  string
+		Extended bool
 	}
 )
 
-var hugoExecutable = "hugo"
+var (
+	hugoExecutable = "hugo"
+)
 
 // Exec executes the plugins functionality
 func (p Plugin) Exec() error {
 	var cmds = make([]*exec.Cmd, 0)
 
+	if p.Config.Extended {
+		hugoExecutable = "hugo-extended"
+	}
+
 	// Check if buildIn plugin version equals
 	// plugin version declared in drone.yml
-	if !versionsEqual(p.BuildInVersion, p.Config.HugoVersion, p.Config.HugoExtended) {
-		hugoVersion := p.Config.HugoVersion
-		if hugoVersion == "" {
-			hugoVersion = p.BuildInVersion
+	if !versionsEqual(p.BuildInVersion, p.Config.Version) {
+		version := p.Config.Version
+
+		if version == "" {
+			version = p.BuildInVersion
 		}
 
-		hugoPath, err := download.Get(hugoVersion, p.Config.HugoExtended)
+		executable, err := download.Get(version, p.Config.Extended)
+
 		if err != nil {
 			return err
 		}
-		hugoExecutable = hugoPath
+
+		hugoExecutable = executable
 	}
+
 	if p.Config.Validate {
 		cmds = append(cmds, commandValidate(p.Config))
 	}
@@ -63,75 +73,66 @@ func (p Plugin) Exec() error {
 
 func commandValidate(config Config) *exec.Cmd {
 	args := []string{"check"}
+
 	if config.Config != "" {
 		args = append(args, "--config", config.Config)
 	}
+
 	return exec.Command(hugoExecutable, args...)
 }
 
 func commandBuild(config Config) *exec.Cmd {
 	var args = make([]string, 0)
 
-	// add bool args
-	if config.BuildDrafts {
+	if config.Drafts {
 		args = append(args, "-D")
 	}
-	if config.BuildExpired {
+
+	if config.Expired {
 		args = append(args, "-E")
 	}
-	if config.BuildFuture {
+
+	if config.Future {
 		args = append(args, "-F")
 	}
-	// add string args
-	if config.CacheDir != "" {
-		args = append(args, "--cacheDir", config.CacheDir)
+
+	if config.Cache != "" {
+		args = append(args, "--cacheDir", config.Cache)
 	}
+
 	if config.Config != "" {
 		args = append(args, "--config", config.Config)
 	}
+
 	if config.Content != "" {
 		args = append(args, "--contentDir", config.Content)
 	}
+
 	if config.Layout != "" {
 		args = append(args, "--layoutDir", config.Layout)
 	}
+
 	if config.Output != "" {
 		args = append(args, "--destination", config.Output)
 	}
+
 	if config.Source != "" {
 		args = append(args, "--source", config.Source)
 	}
+
 	if config.Theme != "" {
 		args = append(args, "--theme", config.Theme)
 	}
-	if config.Url != "" {
-		args = append(args, "--baseURL", config.Url)
+
+	if config.URL != "" {
+		args = append(args, "--baseURL", config.URL)
 	}
 
 	return exec.Command(hugoExecutable, args...)
 }
 
-// trace writes each command to stdout with the command wrapped in an xml
-// tag so that it can be extracted and displayed in the logs.
-func trace(cmd *exec.Cmd) {
-	fmt.Fprintf(os.Stdout, "+ %s\n", strings.Join(cmd.Args, " "))
-}
-
-func versionsEqual(version string, toCompare string, extended bool) bool {
-	if extended {
-		return false
-	}
-
-	if toCompare == version || toCompare == "" {
-		return true
-	} else {
-		return false
-	}
-}
-
 // execAll executes a slice of commands as a batch job
 func execAll(cmds []*exec.Cmd) error {
-	// Execute all commands
 	for _, cmd := range cmds {
 		cmd.Stdout = os.Stdout
 		cmd.Stderr = os.Stderr
@@ -141,5 +142,20 @@ func execAll(cmds []*exec.Cmd) error {
 			return err
 		}
 	}
+
 	return nil
 }
+
+func versionsEqual(version string, toCompare string) bool {
+	if toCompare == version || toCompare == "" {
+		return true
+	}
+
+	return false
+}
+
+// trace writes each command to stdout with the command wrapped in an xml
+// tag so that it can be extracted and displayed in the logs.
+func trace(cmd *exec.Cmd) {
+	fmt.Fprintf(os.Stdout, "+ %s\n", strings.Join(cmd.Args, " "))
+}