move code supporting push, pull, and inspect to libkpod and libkpod/image

Signed-off-by: Ryan Cole <rcyoalne@gmail.com>

libkpod/common/common.go

@@ -0,0 +1,60 @@
+package common
+
+import (
+	"io"
+
+	cp "github.com/containers/image/copy"
+	"github.com/containers/image/types"
+)
+
+// GetCopyOptions constructs a new containers/image/copy.Options{} struct from the given parameters
+func GetCopyOptions(reportWriter io.Writer, signaturePolicyPath string, srcDockerRegistry, destDockerRegistry *DockerRegistryOptions, signing SigningOptions) *cp.Options {
+	if srcDockerRegistry == nil {
+		srcDockerRegistry = &DockerRegistryOptions{}
+	}
+	if destDockerRegistry == nil {
+		destDockerRegistry = &DockerRegistryOptions{}
+	}
+	srcContext := srcDockerRegistry.GetSystemContext(signaturePolicyPath)
+	destContext := destDockerRegistry.GetSystemContext(signaturePolicyPath)
+	return &cp.Options{
+		RemoveSignatures: signing.RemoveSignatures,
+		SignBy:           signing.SignBy,
+		ReportWriter:     reportWriter,
+		SourceCtx:        srcContext,
+		DestinationCtx:   destContext,
+	}
+}
+
+// GetSystemContext Constructs a new containers/image/types.SystemContext{} struct from the given signaturePolicy path
+func GetSystemContext(signaturePolicyPath string) *types.SystemContext {
+	sc := &types.SystemContext{}
+	if signaturePolicyPath != "" {
+		sc.SignaturePolicyPath = signaturePolicyPath
+	}
+	return sc
+}
+
+// CopyStringStringMap deep copies a map[string]string and returns the result
+func CopyStringStringMap(m map[string]string) map[string]string {
+	n := map[string]string{}
+	for k, v := range m {
+		n[k] = v
+	}
+	return n
+}
+
+// IsTrue determines whether the given string equals "true"
+func IsTrue(str string) bool {
+	return str == "true"
+}
+
+// IsFalse determines whether the given string equals "false"
+func IsFalse(str string) bool {
+	return str == "false"
+}
+
+// IsValidBool determines whether the given string equals "true" or "false"
+func IsValidBool(str string) bool {
+	return IsTrue(str) || IsFalse(str)
+}