udpate readme

README.md

@@ -1,6 +1,8 @@
-Argument parsing for Go.
+# Argument parsing for Go
 
 ```golang
+import "github.com/alexflint/go-arg"
+
 var args struct {
 	Foo  string
 	Bar  bool
@@ -16,7 +18,7 @@ hello
 True
 ```
 
-Setting defaults values:
+### Default values
 
 ```golang
 var args struct {
@@ -27,7 +29,7 @@ args.Foo = "default value"
 arg.MustParse(&args)
 ```
 
-Marking options as required
+### Marking options as required
 
 ```golang
 var args struct {
@@ -37,7 +39,7 @@ var args struct {
 arg.MustParse(&args)
 ```
 
-Positional argument:
+### Positional argument
 
 ```golang
 var args struct {
@@ -56,7 +58,7 @@ Input: src.txt
 Output: [x.out y.out z.out]
 ```
 
-Usage strings:
+### Usage strings
 ```bash
 $ ./example -h
 usage: [--verbose] [--dataset DATASET] [--optimize OPTIMIZE] [--help] INPUT [OUTPUT [OUTPUT ...]] 
@@ -73,7 +75,7 @@ options:
 --help, -h               print this help message
 ```
 
-Options with multiple values:
+### Options with multiple values
 ```
 var args struct {
 	Database string

example/example.go

@@ -4,11 +4,11 @@ import "github.com/alexflint/go-arg"
 
 func main() {
 	var args struct {
-		Input            string  `arg:"positional"`
-		Output           string  `arg:"positional"`
-		Foo              string  `arg:"help:this argument is foo"`
-		VeryLongArgument int     `arg:"help:this argument is very long"`
-		Bar              float64 `arg:"-b"`
+		Input    string   `arg:"positional"`
+		Output   []string `arg:"positional"`
+		Verbose  bool     `arg:"-v,help:verbosity level"`
+		Dataset  string   `arg:"help:dataset to use"`
+		Optimize int      `arg:"-O,help:optimization level"`
 	}
 	arg.MustParse(&args)
 }

parse.go

@@ -38,7 +38,7 @@ func Parse(dest ...interface{}) error {
 func ParseFrom(args []string, dest ...interface{}) error {
 	// Add the help option if one is not already defined
 	var internal struct {
-		Help bool `arg:"-h"`
+		Help bool `arg:"-h,help:print this help message"`
 	}
 
 	// Parse the spec

usage.go

@@ -72,7 +72,7 @@ func writeUsage(w io.Writer, specs []*spec) {
 	for _, spec := range positionals {
 		up := strings.ToUpper(spec.long)
 		if spec.multiple {
-			fmt.Fprintf(w, "[%s [%s ...]]", up)
+			fmt.Fprintf(w, "[%s [%s ...]]", up, up)
 		} else {
 			fmt.Fprint(w, up)
 		}