Add self-contained gometalinter build tooling.

tools/vendor/github.com/alecthomas/gometalinter/checkstyle.go

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"encoding/xml"
+	"fmt"
+
+	"gopkg.in/alecthomas/kingpin.v3-unstable"
+)
+
+type checkstyleOutput struct {
+	XMLName xml.Name          `xml:"checkstyle"`
+	Version string            `xml:"version,attr"`
+	Files   []*checkstyleFile `xml:"file"`
+}
+
+type checkstyleFile struct {
+	Name   string             `xml:"name,attr"`
+	Errors []*checkstyleError `xml:"error"`
+}
+
+type checkstyleError struct {
+	Column   int    `xml:"column,attr"`
+	Line     int    `xml:"line,attr"`
+	Message  string `xml:"message,attr"`
+	Severity string `xml:"severity,attr"`
+	Source   string `xml:"source,attr"`
+}
+
+func outputToCheckstyle(issues chan *Issue) int {
+	var lastFile *checkstyleFile
+	out := checkstyleOutput{
+		Version: "5.0",
+	}
+	status := 0
+	for issue := range issues {
+		if lastFile != nil && lastFile.Name != issue.Path {
+			out.Files = append(out.Files, lastFile)
+			lastFile = nil
+		}
+		if lastFile == nil {
+			lastFile = &checkstyleFile{
+				Name: issue.Path,
+			}
+		}
+
+		if config.Errors && issue.Severity != Error {
+			continue
+		}
+
+		lastFile.Errors = append(lastFile.Errors, &checkstyleError{
+			Column:   issue.Col,
+			Line:     issue.Line,
+			Message:  issue.Message,
+			Severity: string(issue.Severity),
+			Source:   issue.Linter.Name,
+		})
+		status = 1
+	}
+	if lastFile != nil {
+		out.Files = append(out.Files, lastFile)
+	}
+	d, err := xml.Marshal(&out)
+	kingpin.FatalIfError(err, "")
+	fmt.Printf("%s%s\n", xml.Header, d)
+	return status
+}