[NO TESTS NEEDED] Vendor in containers/buildah v1.20.0

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

vendor/github.com/containers/buildah/define/pull.go

@@ -0,0 +1,50 @@
+package define
+
+import (
+	"fmt"
+)
+
+// PullPolicy takes the value PullIfMissing, PullAlways, PullIfNewer, or PullNever.
+type PullPolicy int
+
+const (
+	// PullIfMissing is one of the values that BuilderOptions.PullPolicy
+	// can take, signalling that the source image should be pulled from a
+	// registry if a local copy of it is not already present.
+	PullIfMissing PullPolicy = iota
+	// PullAlways is one of the values that BuilderOptions.PullPolicy can
+	// take, signalling that a fresh, possibly updated, copy of the image
+	// should be pulled from a registry before the build proceeds.
+	PullAlways
+	// PullIfNewer is one of the values that BuilderOptions.PullPolicy
+	// can take, signalling that the source image should only be pulled
+	// from a registry if a local copy is not already present or if a
+	// newer version the image is present on the repository.
+	PullIfNewer
+	// PullNever is one of the values that BuilderOptions.PullPolicy can
+	// take, signalling that the source image should not be pulled from a
+	// registry.
+	PullNever
+)
+
+// String converts a PullPolicy into a string.
+func (p PullPolicy) String() string {
+	switch p {
+	case PullIfMissing:
+		return "missing"
+	case PullAlways:
+		return "always"
+	case PullIfNewer:
+		return "ifnewer"
+	case PullNever:
+		return "never"
+	}
+	return fmt.Sprintf("unrecognized policy %d", p)
+}
+
+var PolicyMap = map[string]PullPolicy{
+	"missing": PullIfMissing,
+	"always":  PullAlways,
+	"never":   PullNever,
+	"ifnewer": PullIfNewer,
+}