Isolation strings, should match user input

When we parse isolation we expect users to input chroot, oci, rootless.

So when we translate the constants back to strings, we should use the
same values.

These human names need to be passed over the podman-remote build
bindings, so we need to make them match.

Also docker describes an isolation of "default", which we should also
handle for potential scripts.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

.golangci.yml

@@ -11,7 +11,6 @@ linters:
   disable:
     # All these break for one reason or another
     - dupl
-    - funlen
     - gochecknoglobals
     - gochecknoinits
     - goconst

define/isolation.go

@@ -21,14 +21,12 @@ const (
 // String converts a Isolation into a string.
 func (i Isolation) String() string {
 	switch i {
-	case IsolationDefault:
-		return "IsolationDefault"
-	case IsolationOCI:
-		return "IsolationOCI"
+	case IsolationDefault, IsolationOCI:
+		return "oci"
 	case IsolationChroot:
-		return "IsolationChroot"
+		return "chroot"
 	case IsolationOCIRootless:
-		return "IsolationOCIRootless"
+		return "rootless"
 	}
 	return fmt.Sprintf("unrecognized isolation type %d", i)
 }

define/isolation_test.go

@@ -0,0 +1,35 @@
+package define
+
+import (
+	"testing"
+
+	"github.com/containers/buildah/pkg/parse"
+	"github.com/containers/storage/pkg/unshare"
+)
+
+func TestIsolation(t *testing.T) {
+	isolations := []string{"", "default", "oci", "chroot", "rootless"}
+	for _, i := range isolations {
+		isolation, err := parse.IsolationOption(i)
+		if err != nil {
+			t.Errorf("Isolation %q not supported.", i)
+		}
+		var expected string
+		switch i {
+		case "":
+			if unshare.IsRootless() {
+				expected = "rootless"
+			} else {
+				expected = "oci"
+			}
+		case "default":
+			expected = "oci"
+		default:
+			expected = i
+		}
+
+		if isolation.String() != expected {
+			t.Errorf("Isolation %q not equal to user input %q.", isolation.String(), expected)
+		}
+	}
+}

pkg/parse/parse.go

@@ -959,7 +959,7 @@ func defaultIsolation() (define.Isolation, error) {
 func IsolationOption(isolation string) (define.Isolation, error) {
 	if isolation != "" {
 		switch strings.ToLower(isolation) {
-		case "oci":
+		case "oci", "default":
 			return define.IsolationOCI, nil
 		case "rootless":
 			return define.IsolationOCIRootless, nil