Add support for --compat-auth-file in login/logout

This mostly just inherits the c/common/pkg/auth implementation,
except that AuthFilePath and DockerCompatAuthFilePath can not be set
simultaneously, so don't always set AuthFilePath. c/common already
defaults to the same locations internally.

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

cmd/buildah/login.go

@@ -63,6 +63,10 @@ func loginCmd(c *cobra.Command, args []string, iopts *loginReply) error {
 	if err != nil {
 		return fmt.Errorf("building system context: %w", err)
 	}
+	// parse.SystemContextFromOptions may point this field to an auth.json or to a .docker/config.json;
+	// that’s fair enough for reads, but incorrect for writes (the two files have incompatible formats),
+	// and it interferes with the auth.Login’s own argument parsing.
+	systemContext.AuthFilePath = ""
 	ctx := getContext()
 	iopts.loginOpts.GetLoginSet = c.Flag("get-login").Changed
 	return auth.Login(ctx, systemContext, &iopts.loginOpts, args)

cmd/buildah/logout.go

@@ -51,5 +51,9 @@ func logoutCmd(c *cobra.Command, args []string, iopts *auth.LogoutOptions) error
 	if err != nil {
 		return fmt.Errorf("building system context: %w", err)
 	}
+	// parse.SystemContextFromOptions may point this field to an auth.json or to a .docker/config.json;
+	// that’s fair enough for reads, but incorrect for writes (the two files have incompatible formats),
+	// and it interferes with the auth.Logout’s own argument parsing.
+	systemContext.AuthFilePath = ""
 	return auth.Logout(systemContext, iopts, args)
 }

docs/buildah-login.1.md

@@ -29,6 +29,10 @@ Path of the authentication file. Default is ${XDG_\RUNTIME\_DIR}/containers/auth
 Note: You can also override the default path of the authentication file by setting the REGISTRY\_AUTH\_FILE
 environment variable. `export REGISTRY_AUTH_FILE=path`
 
+**--compat-auth-file**=*path*
+
+Instead of updating the default credentials file, update the one at *path*, and use a Docker-compatible format.
+
 **--cert-dir** *path*
 
 Use certificates at *path* (\*.crt, \*.cert, \*.key) to connect to the registry.

docs/buildah-logout.1.md

@@ -31,6 +31,10 @@ Path of the authentication file. Default is ${XDG_\RUNTIME\_DIR}/containers/auth
 Note: You can also override the default path of the authentication file by setting the REGISTRY\_AUTH\_FILE
 environment variable. `export REGISTRY_AUTH_FILE=path`
 
+**--compat-auth-file**=*path*
+
+Instead of updating the default credentials file, update the one at *path*, and use a Docker-compatible format.
+
 **--help**, **-h**
 
 Print usage statement