chore: update CLI usages

check.go

@@ -24,9 +24,11 @@ import (
 )
 
 var (
-	checkCmd = &cobra.Command{
-		Use:   "check <package>",
-		Short: "Checks whether licenses for a package are not Forbidden.",
+	checkHelp = "Checks whether licenses for a package are not Forbidden."
+	checkCmd  = &cobra.Command{
+		Use:   "check <package> [package...]",
+		Short: checkHelp,
+		Long:  checkHelp + packageHelp,
 		Args:  cobra.MinimumNArgs(1),
 		RunE:  checkMain,
 	}

csv.go

@@ -25,9 +25,11 @@ import (
 )
 
 var (
-	csvCmd = &cobra.Command{
-		Use:   "csv <package>",
-		Short: "Prints all licenses that apply to a Go package and its dependencies",
+	csvHelp = "Prints all licenses that apply to one or more Go packages and their dependencies."
+	csvCmd  = &cobra.Command{
+		Use:   "csv <package> [package...]",
+		Short: csvHelp,
+		Long:  csvHelp + packageHelp,
 		Args:  cobra.MinimumNArgs(1),
 		RunE:  csvMain,
 	}

main.go

@@ -26,11 +26,26 @@ import (
 
 var (
 	rootCmd = &cobra.Command{
-		Use: "licenses",
+		Use:   "go-licenses",
+		Short: "go-licenses helps you work with licenses of your go project's dependencies.",
+		Long: `go-licenses helps you work with licenses of your go project's dependencies.
+
+Prerequisites:
+1. Go v1.16 or later.
+2. Change directory to your go project.
+3. Run "go mod download".`,
 	}
 
 	// Flags shared between subcommands
 	confidenceThreshold float64
+	packageHelp         = `
+
+Typically, specify the Go package that builds your Go binary.
+go-licenses expects the same package argument format as "go build".
+For example:
+* A rooted import path like "github.com/google/go-licenses" or "github.com/google/go-licenses/licenses".
+* A relative path that denotes the package in that directory, like "." or "./cmd/some-command".
+To learn more about Go package argument, run "go help packages".`
 )
 
 func init() {

save.go

@@ -30,9 +30,11 @@ import (
 )
 
 var (
-	saveCmd = &cobra.Command{
-		Use:   "save <package>",
-		Short: "Saves licenses, copyright notices and source code, as required by a Go package's dependencies, to a directory.",
+	saveHelp = "Saves licenses, copyright notices and source code, as required by a Go package's dependencies, to a directory."
+	saveCmd  = &cobra.Command{
+		Use:   "save <package> [package...]",
+		Short: saveHelp,
+		Long:  saveHelp + packageHelp,
 		Args:  cobra.MinimumNArgs(1),
 		RunE:  saveMain,
 	}