replace logger interface with anchore/go-logger (#1279)

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

internal/log/log.go

@@ -3,10 +3,13 @@ Package log contains the singleton object and helper functions for facilitating
 */
 package log
 
-import "github.com/anchore/syft/syft/logger"
+import (
+	"github.com/anchore/go-logger"
+	"github.com/anchore/go-logger/adapter/discard"
+)
 
 // Log is the singleton used to facilitate logging internally within syft
-var Log logger.Logger = &nopLogger{}
+var Log logger.Logger = discard.New()
 
 // Errorf takes a formatted template string and template arguments for the error logging level.
 func Errorf(format string, args ...interface{}) {
@@ -47,3 +50,23 @@ func Debugf(format string, args ...interface{}) {
 func Debug(args ...interface{}) {
 	Log.Debug(args...)
 }
+
+// Tracef takes a formatted template string and template arguments for the trace logging level.
+func Tracef(format string, args ...interface{}) {
+	Log.Tracef(format, args...)
+}
+
+// Trace logs the given arguments at the trace logging level.
+func Trace(args ...interface{}) {
+	Log.Trace(args...)
+}
+
+// WithFields returns a message logger with multiple key-value fields.
+func WithFields(fields ...interface{}) logger.MessageLogger {
+	return Log.WithFields(fields...)
+}
+
+// Nested returns a new logger with hard coded key-value pairs
+func Nested(fields ...interface{}) logger.Logger {
+	return Log.Nested(fields...)
+}

internal/log/nop.go

@@ -1,12 +0,0 @@
-package log
-
-type nopLogger struct{}
-
-func (l *nopLogger) Errorf(format string, args ...interface{}) {}
-func (l *nopLogger) Error(args ...interface{})                 {}
-func (l *nopLogger) Warnf(format string, args ...interface{})  {}
-func (l *nopLogger) Warn(args ...interface{})                  {}
-func (l *nopLogger) Infof(format string, args ...interface{})  {}
-func (l *nopLogger) Info(args ...interface{})                  {}
-func (l *nopLogger) Debugf(format string, args ...interface{}) {}
-func (l *nopLogger) Debug(args ...interface{})                 {}