migrate to github.com/moby/go-archive module

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

vendor/github.com/moby/go-archive/wrap.go

@@ -0,0 +1,59 @@
+package archive
+
+import (
+	"archive/tar"
+	"bytes"
+	"io"
+)
+
+// Generate generates a new archive from the content provided
+// as input.
+//
+// `files` is a sequence of path/content pairs. A new file is
+// added to the archive for each pair.
+// If the last pair is incomplete, the file is created with an
+// empty content. For example:
+//
+// Generate("foo.txt", "hello world", "emptyfile")
+//
+// The above call will return an archive with 2 files:
+//   - ./foo.txt with content "hello world"
+//   - ./empty with empty content
+//
+// FIXME: stream content instead of buffering
+// FIXME: specify permissions and other archive metadata
+func Generate(input ...string) (io.Reader, error) {
+	files := parseStringPairs(input...)
+	buf := new(bytes.Buffer)
+	tw := tar.NewWriter(buf)
+	for _, file := range files {
+		name, content := file[0], file[1]
+		hdr := &tar.Header{
+			Name: name,
+			Size: int64(len(content)),
+		}
+		if err := tw.WriteHeader(hdr); err != nil {
+			return nil, err
+		}
+		if _, err := tw.Write([]byte(content)); err != nil {
+			return nil, err
+		}
+	}
+	if err := tw.Close(); err != nil {
+		return nil, err
+	}
+	return buf, nil
+}
+
+func parseStringPairs(input ...string) [][2]string {
+	output := make([][2]string, 0, len(input)/2+1)
+	for i := 0; i < len(input); i += 2 {
+		var pair [2]string
+		pair[0] = input[i]
+		if i+1 < len(input) {
+			pair[1] = input[i+1]
+		}
+		output = append(output, pair)
+	}
+	return output
+}