Add support for Fulcio and Rekor, and --sign-by-sigstore=param-file

(skopeo copy) and (skopeo sync) now support --sign-by-sigstore=param-file,
using the containers-sigstore-signing-params.yaml(5) file format.

That notably adds support for Fulcio and Rekor signing.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/github.com/skratchdot/open-golang/open/open.go

@@ -0,0 +1,50 @@
+/*
+
+	Open a file, directory, or URI using the OS's default
+	application for that object type.  Optionally, you can
+	specify an application to use.
+
+	This is a proxy for the following commands:
+
+	         OSX: "open"
+	     Windows: "start"
+	 Linux/Other: "xdg-open"
+
+	This is a golang port of the node.js module: https://github.com/pwnall/node-open
+
+*/
+package open
+
+/*
+	Open a file, directory, or URI using the OS's default
+	application for that object type. Wait for the open
+	command to complete.
+*/
+func Run(input string) error {
+	return open(input).Run()
+}
+
+/*
+	Open a file, directory, or URI using the OS's default
+	application for that object type. Don't wait for the
+	open command to complete.
+*/
+func Start(input string) error {
+	return open(input).Start()
+}
+
+/*
+	Open a file, directory, or URI using the specified application.
+	Wait for the open command to complete.
+*/
+func RunWith(input string, appName string) error {
+	return openWith(input, appName).Run()
+}
+
+/*
+	Open a file, directory, or URI using the specified application.
+	Don't wait for the open command to complete.
+*/
+func StartWith(input string, appName string) error {
+	return openWith(input, appName).Start()
+}