Grand test fixup (#138)

* start fixing up tests

* fix up tests + automate with drone

* fiddle with linting

* messing about with drone.yml

* some more fiddling

* hmmm

* add cache

* add vendor directory

* verbose

* ci updates

* update some little things

* update sig

vendor/github.com/dsoprea/go-exif/v2/common/utility.go

@@ -0,0 +1,79 @@
+package exifcommon
+
+import (
+	"bytes"
+	"fmt"
+	"time"
+
+	"github.com/dsoprea/go-logging"
+)
+
+// DumpBytes prints a list of hex-encoded bytes.
+func DumpBytes(data []byte) {
+	fmt.Printf("DUMP: ")
+	for _, x := range data {
+		fmt.Printf("%02x ", x)
+	}
+
+	fmt.Printf("\n")
+}
+
+// DumpBytesClause prints a list like DumpBytes(), but encapsulated in
+// "[]byte { ... }".
+func DumpBytesClause(data []byte) {
+	fmt.Printf("DUMP: ")
+
+	fmt.Printf("[]byte { ")
+
+	for i, x := range data {
+		fmt.Printf("0x%02x", x)
+
+		if i < len(data)-1 {
+			fmt.Printf(", ")
+		}
+	}
+
+	fmt.Printf(" }\n")
+}
+
+// DumpBytesToString returns a stringified list of hex-encoded bytes.
+func DumpBytesToString(data []byte) string {
+	b := new(bytes.Buffer)
+
+	for i, x := range data {
+		_, err := b.WriteString(fmt.Sprintf("%02x", x))
+		log.PanicIf(err)
+
+		if i < len(data)-1 {
+			_, err := b.WriteRune(' ')
+			log.PanicIf(err)
+		}
+	}
+
+	return b.String()
+}
+
+// DumpBytesClauseToString returns a comma-separated list of hex-encoded bytes.
+func DumpBytesClauseToString(data []byte) string {
+	b := new(bytes.Buffer)
+
+	for i, x := range data {
+		_, err := b.WriteString(fmt.Sprintf("0x%02x", x))
+		log.PanicIf(err)
+
+		if i < len(data)-1 {
+			_, err := b.WriteString(", ")
+			log.PanicIf(err)
+		}
+	}
+
+	return b.String()
+}
+
+// ExifFullTimestampString produces a string like "2018:11:30 13:01:49" from a
+// `time.Time` struct. It will attempt to convert to UTC first.
+func ExifFullTimestampString(t time.Time) (fullTimestampPhrase string) {
+	t = t.UTC()
+
+	return fmt.Sprintf("%04d:%02d:%02d %02d:%02d:%02d", t.Year(), t.Month(), t.Day(), t.Hour(), t.Minute(), t.Second())
+}