cmd/capabilities: expose capabilities through CLI (#4588)

There is a new command argument "capabilities". With this, it is
possible to print the current capabilities version, show all
capabilities versions & print any capabilities version, without the need
of a file. Moreover, for the other commands which use the --capabilities
flag, it is possible to give only the version number, without specifying
a file. However, there are no breaking changes for those who use the
capabilities file as an input for the flag. Unit tests were also
written, in order to test the new argument and the changes made in ast.

Fixes: #4236

Signed-off-by: IoannisMatzaris <matzarisioannis@gmail.com>

cmd/flags.go

@@ -6,7 +6,6 @@ package cmd
 
 import (
 	"fmt"
-	"os"
 
 	"github.com/spf13/pflag"
 
@@ -127,7 +126,7 @@ func addBundleVerificationExcludeFilesFlag(fs *pflag.FlagSet, excludeNames *[]st
 }
 
 func addCapabilitiesFlag(fs *pflag.FlagSet, f *capabilitiesFlag) {
-	fs.VarP(f, "capabilities", "", "set capabilities.json file path")
+	fs.VarP(f, "capabilities", "", "set capabilities version or capabilities.json file path")
 }
 
 func addPartialFlag(fs *pflag.FlagSet, partial *bool, value bool) {
@@ -170,8 +169,8 @@ func setExplainFlag(fs *pflag.FlagSet, explain *util.EnumFlag) {
 }
 
 type capabilitiesFlag struct {
-	C    *ast.Capabilities
-	path string
+	C             *ast.Capabilities
+	pathOrVersion string
 }
 
 func newcapabilitiesFlag() *capabilitiesFlag {
@@ -187,18 +186,23 @@ func (f *capabilitiesFlag) Type() string {
 }
 
 func (f *capabilitiesFlag) String() string {
-	return f.path
+	return f.pathOrVersion
 }
 
 func (f *capabilitiesFlag) Set(s string) error {
-	f.path = s
-	fd, err := os.Open(s)
-	if err != nil {
-		return err
+	f.pathOrVersion = s
+	var errPath, errVersion error
+
+	f.C, errPath = ast.LoadCapabilitiesFile(s)
+	if errPath != nil {
+		f.C, errVersion = ast.LoadCapabilitiesVersion(s)
 	}
-	defer fd.Close()
-	f.C, err = ast.LoadCapabilitiesJSON(fd)
-	return err
+
+	if errVersion != nil && errPath != nil {
+		return fmt.Errorf("no such file or capabilities version found: %v", s)
+	}
+	return nil
+
 }
 
 type stringptrFlag struct {