Add help command, ensure -help works on all commands.

fixes #91

Author: stapelberg

create_salsa_project.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"flag"
+	"fmt"
 	"io/ioutil"
 	"log"
 	"net/http"
@@ -10,15 +11,20 @@ import (
 )
 
 func execCreateSalsaProject(args []string) {
-	fs := flag.NewFlagSet("search", flag.ExitOnError)
+	fs := flag.NewFlagSet("create-salsa-project", flag.ExitOnError)
+
+	fs.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage: %s create-salsa-project <project-name>\n", os.Args[0])
+		fmt.Fprintf(os.Stderr, "Example: %s create-salsa-project golang-github-mattn-go-sqlite3\n", os.Args[0])
+	}
 
 	if err := fs.Parse(args); err != nil {
 		log.Fatal(err)
 	}
 
 	if fs.NArg() != 1 {
-		log.Printf("Usage: %s create-salsa-project <project-name>\n", os.Args[0])
-		log.Fatalf("Example: %s create-salsa-project golang-github-mattn-go-sqlite3\n", os.Args[0])
+		fs.Usage()
+		os.Exit(1)
 	}
 
 	projectName := fs.Arg(0)

estimate.go

@@ -117,17 +117,21 @@ func estimate(importpath string) error {
 }
 
 func execEstimate(args []string) {
-	fs := flag.NewFlagSet("search", flag.ExitOnError)
+	fs := flag.NewFlagSet("estimate", flag.ExitOnError)
+
+	fs.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage: %s estimate <go-package-importpath>\n", os.Args[0])
+		fmt.Fprintf(os.Stderr, "Estimates the work necessary to bring <go-package-importpath> into Debian by printing all currently unpacked repositories\n")
+		fmt.Fprintf(os.Stderr, "Example: %s estimate github.com/Debian/dh-make-golang\n", os.Args[0])
+	}
 
 	err := fs.Parse(args)
 	if err != nil {
 		log.Fatal(err)
 	}
 
 	if fs.NArg() != 1 {
-		fmt.Fprintf(os.Stderr, "Usage: %s estimate <importpath>\n", os.Args[0])
-		fmt.Fprintf(os.Stderr, "Estimates the work necessary to bring <importpath> into Debian by printing all currently unpacked repositories\n")
-		fmt.Fprintf(os.Stderr, "Example: %s estimate github.com/Debian/dh-make-golang\n", os.Args[0])
+		fs.Usage()
 		os.Exit(1)
 	}
 

main.go

@@ -1,9 +1,23 @@
 package main
 
 import (
+	"fmt"
 	"os"
 )
 
+func usage() {
+	fmt.Fprintf(os.Stderr, "Usage: %s [globalflags] <command> [flags] <args>\n", os.Args[0])
+	fmt.Fprintf(os.Stderr, "\n")
+	fmt.Fprintf(os.Stderr, "%s commands:\n", os.Args[0])
+	fmt.Fprintf(os.Stderr, "\tmake\t\t\tcreate a Debian package\n")
+	fmt.Fprintf(os.Stderr, "\tsearch\t\t\tsearch Debian for already-existing packages\n")
+	fmt.Fprintf(os.Stderr, "\testimate\t\testimate the amount of work for a package\n")
+	fmt.Fprintf(os.Stderr, "\tcreate-salsa-project\tcreate a project for hosting Debian packaging\n")
+	fmt.Fprintf(os.Stderr, "\n")
+	fmt.Fprintf(os.Stderr, "For backwards compatibility, when no command is specified, the make command is executed.\n")
+	fmt.Fprintf(os.Stderr, "To learn more about a command, run %s <command> -help, e.g. %s make -help\n", os.Args[0], os.Args[0])
+}
+
 func main() {
 	// Retrieve args and Shift binary name off argument list.
 	args := os.Args[1:]
@@ -15,14 +29,18 @@ func main() {
 	}
 
 	switch cmd {
+	case "help":
+		usage()
 	case "search":
 		execSearch(args[1:])
 	case "create-salsa-project":
 		execCreateSalsaProject(args[1:])
 	case "estimate":
 		execEstimate(args[1:])
+	case "make":
+		execMake(args[1:], nil)
 	default:
-		execMake(args)
+		// redirect -help to the global usage
+		execMake(args, usage)
 	}
-
 }

make.go

@@ -682,8 +682,22 @@ func copyFile(src, dest string) error {
 	return output.Close()
 }
 
-func execMake(args []string) {
+func execMake(args []string, usage func()) {
 	fs := flag.NewFlagSet("make", flag.ExitOnError)
+	if usage != nil {
+		fs.Usage = usage
+	} else {
+		fs.Usage = func() {
+			fmt.Fprintf(os.Stderr, "Usage: %s [make] <go-package-importpath>\n", os.Args[0])
+			fmt.Fprintf(os.Stderr, "Example: %s make golang.org/x/oauth2\n", os.Args[0])
+			fmt.Fprintf(os.Stderr, "\n")
+			fmt.Fprintf(os.Stderr, "%s will create new files and directories in the current working directory.\n", os.Args[0])
+			fmt.Fprintf(os.Stderr, "%s will connect to the internet to download the specified Go package.\n", os.Args[0])
+			fmt.Fprintf(os.Stderr, "\n")
+			fmt.Fprintf(os.Stderr, "Flags:\n")
+			fs.PrintDefaults()
+		}
+	}
 
 	var gitRevision string
 	fs.StringVar(&gitRevision,
@@ -709,11 +723,7 @@ func execMake(args []string) {
 	}
 
 	if fs.NArg() < 1 {
-		fmt.Fprintf(os.Stderr, "Usage: %s <go-package-name>\n", os.Args[0])
-		fmt.Fprintf(os.Stderr, "Example: %s golang.org/x/oauth2\n", os.Args[0])
-		fmt.Fprintf(os.Stderr, "\n")
-		fmt.Fprintf(os.Stderr, "%s will create new files and directories in the current working directory.\n", os.Args[0])
-		fmt.Fprintf(os.Stderr, "%s will connect to the internet to download the specified Go package and its dependencies.\n", os.Args[0])
+		fs.Usage()
 		os.Exit(1)
 	}
 

search.go

@@ -48,15 +48,19 @@ func getGolangBinaries() (map[string]string, error) {
 func execSearch(args []string) {
 	fs := flag.NewFlagSet("search", flag.ExitOnError)
 
+	fs.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage: %s search <pattern>\n", os.Args[0])
+		fmt.Fprintf(os.Stderr, "Uses Go's default regexp syntax (https://golang.org/pkg/regexp/syntax/)\n")
+		fmt.Fprintf(os.Stderr, "Example: %s search 'debi.*'\n", os.Args[0])
+	}
+
 	err := fs.Parse(args)
 	if err != nil {
 		log.Fatal(err)
 	}
 
 	if fs.NArg() != 1 {
-		fmt.Fprintf(os.Stderr, "Usage: %s search <pattern>\n", os.Args[0])
-		fmt.Fprintf(os.Stderr, "Uses Go's default regexp syntax (https://golang.org/pkg/regexp/syntax/)\n")
-		fmt.Fprintf(os.Stderr, "Example: %s search debi.*\n", os.Args[0])
+		fs.Usage()
 		os.Exit(1)
 	}