Add --version and --help flags to executables

HomebrewFormula/age.rb

@@ -13,8 +13,9 @@ class Age < Formula
   depends_on "go" => :build
 
   def install
+
     mkdir bin
-    system "go", "build", "-trimpath", "-o", bin, "filippo.io/age/cmd/..."
+    system "go", "build", "-trimpath", "-o", bin, "-ldflags", "-X main.version=v#{version}", "filippo.io/age/cmd/..."
     prefix.install_metafiles
   end
 end

README.md

@@ -29,6 +29,8 @@ Options:
     -r, --recipient RECIPIENT   Encrypt to the specified RECIPIENT. Can be repeated.
     -d, --decrypt               Decrypt the input to the output.
     -i, --identity KEY          Use the private key file at path KEY. Can be repeated.
+    -h, --help                  Print this message and exit
+    --version                   Print the version string and exit
 
 INPUT defaults to standard input, and OUTPUT defaults to standard output.
 
@@ -89,8 +91,13 @@ If your system has [Go 1.13+](https://golang.org/dl/), you can build from source
 
 ```
 git clone https://filippo.io/age && cd age
-go build -o . filippo.io/age/cmd/...
+./build_age #(Use build_age.ps1 with Powershell)  
 ```
+The build script is just a wrapper around `go build` that automatically inserts version information. The same result can be achieved by running:  
+```
+go build --ldflags "-X main.version=$VERSION -X main.commit=$HASH" -o . filippo.io/age/cmd/...
+```  
+Where `$VERSION` is the current git tag and `$HASH` is the current (short) git hash  
 
 On Arch Linux, age is available from AUR as [`age`](https://aur.archlinux.org/packages/age/) or [`age-git`](https://aur.archlinux.org/packages/age-git/):
 

build_age

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+function usage() {
+  echo "usage: ./build_age [--release]"
+  exit 1
+}
+# --release doesn't use a hash to allow for minor post-tag commits (e.g. README updates) without having to revert or retag
+if [[ $# -eq 1 ]] && [[ $1 == "--release" ]]; then
+  AGE_VER=$(git describe --tags)
+elif [[ $# -ne 0 ]]; then
+  usage
+else
+  AV=$(git describe --tags)
+  AGE_VER=${AV%-*-g*}
+  AGE_COMMIT=$(git rev-parse --short HEAD)
+fi
+
+go build --ldflags "-X main.version=$AGE_VER -X main.commit=$AGE_COMMIT" -o . filippo.io/age/cmd/...
+if [[ $? ]]; then
+  echo "age build success"
+else
+  echo "age build failure"
+  exit 1
+fi
+

build_age.ps1

@@ -0,0 +1,26 @@
+param([switch] $release = $false)
+
+if($args.count -ne 0){
+    Write-Output "Usage: ./build_age.ps1 [-release]"
+    exit 1
+}
+
+$AV=git describe --tags
+$AV=$AV -split '-\d*-g'
+$AGE_VER=$av[0]
+# -release doesn't use a hash to allow for minor post-tag commits (e.g. README updates) without having to revert or retag
+if($release.IsPresent){
+    $verstring="`"-X main.version=$AGE_VER`""
+} else{
+    $verstring="`"-X main.version=$AGE_VER -X main.commit=$($AV[1])`""
+}
+
+go build --ldflags $verstring -o . filippo.io/age/cmd/...
+
+if($?){
+    Write-Output "build success"
+} else{
+    Write-Output "build failure"
+    exit 1
+}
+

cmd/age-keygen/keygen.go

@@ -17,13 +17,51 @@ import (
 	"golang.org/x/crypto/ssh/terminal"
 )
 
+var version = "not compiled with version information"
+var commit string
+
+const usage = `Usage:
+    age-keygen
+    age-keygen -o OUTPUT
+
+Options:
+    -o OUTPUT         Write the result to the file at path OUTPUT.
+    -h, --help        Print this message and exit
+    --version     Print the version string and exit
+
+If -o is not provided, OUTPUT defaults to standard output
+
+Example:
+    $ age-keygen -o key.txt
+    Public key: age12d695gkxyk07dfng0ght8thsc9yhug74um2hnydslpunjvjpvd7s3dzp6m
+    $ cat key.txt|grep KEY
+    AGE-SECRET-KEY-1L3W64GQX6H8YPG7HXW7EMTXHSJ97Q3G8HGGPXS2N5PRT9H6TDD6S7LRZZS`
+
 func main() {
 	log.SetFlags(0)
+	flag.Usage = func() { fmt.Fprintf(os.Stderr, "%s\n", usage) }
 
+	var verFlag, helpFlag bool
+	flag.BoolVar(&verFlag, "version", false, "print version and quit")
+	flag.BoolVar(&helpFlag, "h", false, "print usage and quit")
+	flag.BoolVar(&helpFlag, "help", false, "print usage and quit")
 	outFlag := flag.String("o", "", "output to `FILE` (default stdout)")
 	flag.Parse()
+	switch {
+	case helpFlag:
+		fmt.Printf("%s\n", usage)
+		os.Exit(0)
+	case verFlag:
+		if commit != "" {
+			fmt.Printf("Version: %s\nHash: %s\n", version, commit)
+		} else {
+			fmt.Printf("Version: %s\n", version)
+		}
+		os.Exit(0)
+	}
 	if len(flag.Args()) != 0 {
-		log.Fatalf("age-keygen takes no arguments")
+		log.Fatalf("age-keygen takes no arguments.\n"+
+			"Run age-keygen -h for help")
 	}
 
 	out := os.Stdout

cmd/age/age.go

@@ -28,6 +28,9 @@ func (f *multiFlag) Set(value string) error {
 	return nil
 }
 
+var version = "not compiled with version information"
+var commit string
+
 const usage = `Usage:
     age -r RECIPIENT [-a] [-o OUTPUT] [INPUT]
     age --decrypt [-i KEY] [-o OUTPUT] [INPUT]
@@ -39,6 +42,8 @@ Options:
     -r, --recipient RECIPIENT   Encrypt to the specified RECIPIENT. Can be repeated.
     -d, --decrypt               Decrypt the input to the output.
     -i, --identity KEY          Use the private key file at path KEY. Can be repeated.
+    -h, --help                  Print this message and exit
+    --version                   Print the version string and exit
 
 INPUT defaults to standard input, and OUTPUT defaults to standard output.
 
@@ -60,9 +65,9 @@ func main() {
 	flag.Usage = func() { fmt.Fprintf(os.Stderr, "%s\n", usage) }
 
 	var (
-		outFlag                          string
-		decryptFlag, armorFlag, passFlag bool
-		recipientFlags, identityFlags    multiFlag
+		outFlag                                             string
+		decryptFlag, armorFlag, passFlag, verFlag, helpFlag bool
+		recipientFlags, identityFlags                       multiFlag
 	)
 
 	flag.BoolVar(&decryptFlag, "d", false, "decrypt the input")
@@ -77,13 +82,30 @@ func main() {
 	flag.Var(&recipientFlags, "recipient", "recipient (can be repeated)")
 	flag.Var(&identityFlags, "i", "identity (can be repeated)")
 	flag.Var(&identityFlags, "identity", "identity (can be repeated)")
+	flag.BoolVar(&verFlag, "version", false, "print version and quit")
+	flag.BoolVar(&helpFlag, "h", false, "print usage and quit")
+	flag.BoolVar(&helpFlag, "help", false, "print usage and quit")
 	flag.Parse()
 
-	if flag.NArg() > 1 {
+	if flag.NArg()+flag.NFlag() == 0 {
+		logFatalf("%s\n", usage)
+	} else if flag.NArg() > 1 {
 		logFatalf("Error: too many arguments.\n" +
-			"age accepts a single optional argument for the input file.")
+			"age accepts a single optional argument for the input file.\n" +
+			"Run age -h for help")
 	}
+
 	switch {
+	case helpFlag:
+		fmt.Printf("%s\n", usage)
+		os.Exit(0)
+	case verFlag:
+		if commit != "" {
+			fmt.Printf("Version: %s\nHash: %s\n", version, commit)
+		} else {
+			fmt.Printf("Version: %s\n", version)
+		}
+		os.Exit(0)
 	case decryptFlag:
 		if armorFlag {
 			logFatalf("Error: -a/--armor can't be used with -d/--decrypt.\n" +