bugfix: Add back default cmd.RootCommand definition. (#7811)

This commit fixes an issue when upgrading codebases to OPA v1.7.0.

In PR #7797, we introduced the ability to provide "branding"
information in OPA commands and help messages, which would
allow easier customized OPA distributions in the future.

However, this changeset removed the public symbol `cmd.RootCommand`,
and required refactoring to use `cmd.Command`, which breaks automated
upgrades, such as those done by Dependabot.

This PR adds back the missing symbol, with the original/default "OPA"
branding provided. This should allow existing codebases to upgrade
without requiring any code changes.

Signed-off-by: Philip Conrad <philip@chariot-chaser.net>

Author: philipaconrad

build/generate-man/generate.go

@@ -23,7 +23,7 @@ func main() {
 		log.Fatal(err)
 	}
 
-	cmd := cmd.Command(nil, "OPA")
+	cmd := cmd.RootCommand
 	cmd.Use = "opa [command]"
 	cmd.DisableAutoGenTag = true
 

cmd/commands.go

@@ -10,6 +10,9 @@ import (
 	iversion "github.com/open-policy-agent/opa/internal/version"
 )
 
+// Backwards compatibility definition. Newer code should use Command.
+var RootCommand = Command(nil, "OPA")
+
 // UserAgent lets you override the OPA UA sent with all the HTTP requests.
 // It's another vanity thing -- if you build your own version of OPA, you
 // may want to adjust this.

main.go

@@ -19,8 +19,7 @@ func main() {
 		}
 	}() // orderly shutdown, run all defer routines
 
-	root := cmd.Command(nil, "OPA")
-	if err := root.Execute(); err != nil {
+	if err := cmd.RootCommand.Execute(); err != nil {
 		var e *cmd.ExitError
 		if errors.As(err, &e) {
 			exit = e.Exit