Add --no-creds flag to skopeo inspect

Follow PR #433
Close #421

Currently skopeo inspect allows to:
Use the default credentials in $HOME/.docker.config
Explicitly define credentials via de --creds flag

This implements a --no-creds flag which will query docker registries anonymously.

Signed-off-by: Qi Wang <qiwan@redhat.com>

cmd/skopeo/utils.go

@@ -63,6 +63,7 @@ type imageOptions struct {
 	tlsVerify        optionalBool        // Require HTTPS and verify certificates (for docker: and docker-daemon:)
 	sharedBlobDir    string              // A directory to use for OCI blobs, shared across repositories
 	dockerDaemonHost string              // docker-daemon: host to connect to
+	noCreds          bool                // Access the registry anonymously
 }
 
 // imageFlags prepares a collection of CLI flags writing into imageOptions, and the managed imageOptions structure.
@@ -105,6 +106,11 @@ func imageFlags(global *globalOptions, shared *sharedImageOptions, flagPrefix, c
 			Usage:       "use docker daemon host at `HOST` (docker-daemon: only)",
 			Destination: &opts.dockerDaemonHost,
 		},
+		cli.BoolFlag{
+			Name:        flagPrefix + "no-creds",
+			Usage:       "Access the registry anonymously",
+			Destination: &opts.noCreds,
+		},
 	}, &opts
 }
 
@@ -132,6 +138,9 @@ func (opts *imageOptions) newSystemContext() (*types.SystemContext, error) {
 	if opts.tlsVerify.present {
 		ctx.DockerInsecureSkipTLSVerify = types.NewOptionalBool(!opts.tlsVerify.value)
 	}
+	if opts.credsOption.present && opts.noCreds {
+		return nil, errors.New("creds and no-creds cannot be specified at the same time")
+	}
 	if opts.credsOption.present {
 		var err error
 		ctx.DockerAuthConfig, err = getDockerAuth(opts.credsOption.value)
@@ -139,6 +148,9 @@ func (opts *imageOptions) newSystemContext() (*types.SystemContext, error) {
 			return nil, err
 		}
 	}
+	if opts.noCreds {
+		ctx.DockerAuthConfig = &types.DockerAuthConfig{}
+	}
 	return ctx, nil
 }
 

completions/bash/skopeo

@@ -55,6 +55,8 @@ _skopeo_copy() {
     local boolean_options="
     --dest-compress
     --remove-signatures
+    --src-no-creds
+    --dest-no-creds
     "
 
     local transports="
@@ -73,6 +75,7 @@ _skopeo_inspect() {
      local boolean_options="
      --raw
      --tls-verify
+     --no-creds
     "
 
     local transports="
@@ -115,6 +118,7 @@ _skopeo_delete() {
      "
      local boolean_options="
      --tls-verify
+     --no-creds
      "
 
     local transports="

docs/skopeo-copy.1.md

@@ -38,10 +38,14 @@ If the authorization state is not found there, $HOME/.docker/config.json is chec
 
 **--src-cert-dir** _path_ Use certificates at _path_ (*.crt, *.cert, *.key) to connect to the source registry or daemon
 
+**--src-no-creds** _bool-value_ Access the registry anonymously.
+
 **--src-tls-verify** _bool-value_ Require HTTPS and verify certificates when talking to container source registry or daemon (defaults to true)
 
 **--dest-cert-dir** _path_ Use certificates at _path_ (*.crt, *.cert, *.key) to connect to the destination registry or daemon
 
+**--dest-no-creds** _bool-value_  Access the registry anonymously.
+
 **--dest-ostree-tmp-dir** _path_ Directory to use for OSTree temporary files.
 
 **--dest-tls-verify** _bool-value_ Require HTTPS and verify certificates when talking to container destination registry or daemon (defaults to true)

docs/skopeo-delete.1.md

@@ -1,7 +1,7 @@
 % skopeo-delete(1)
 
 ## NAME
-skopeo\-delete - Mark _image-name_ for deletion.  
+skopeo\-delete - Mark _image-name_ for deletion.
 
 ## SYNOPSIS
 **skopeo delete** _image-name_
@@ -30,6 +30,8 @@ $ docker exec -it registry /usr/bin/registry garbage-collect /etc/docker-distrib
 
 **--tls-verify** _bool-value_ Require HTTPS and verify certificates when talking to container registries (defaults to true)
 
+**--no-creds** _bool-value_ Access the registry anonymously.
+
 Additionally, the registry must allow deletions by setting `REGISTRY_STORAGE_DELETE_ENABLED=true` for the registry daemon.
 
 ## EXAMPLES

docs/skopeo-inspect.1.md

@@ -23,6 +23,8 @@ Return low-level information about _image-name_ in a registry
 
   **--tls-verify** _bool-value_ Require HTTPS and verify certificates when talking to container registries (defaults to true)
 
+  **--no-creds** _bool-value_ Access the registry anonymously.
+
 ## EXAMPLES
 
 To review information for the image fedora from the docker.io registry:

vendor/github.com/kr/pretty/go.mod

@@ -0,0 +1,3 @@
+module "github.com/kr/pretty"
+
+require "github.com/kr/text" v0.1.0

vendor/github.com/kr/text/go.mod

@@ -0,0 +1,3 @@
+module "github.com/kr/text"
+
+require "github.com/kr/pty" v1.1.1

vendor/golang.org/x/text/go.mod

@@ -0,0 +1,3 @@
+module golang.org/x/text
+
+require golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e