cmd,extra: restore the Version link-time variable

We don't need it in our builds, but it's useful for downstream packagers.

Fixes #671
Updates NixOS/nixpkgs#474666
Updates golang/go#77020

extra/age-plugin-pq/plugin-pq.go

@@ -30,12 +30,16 @@ implementation of age that supports plugins.
 Recipients work out of the box, while identities need to be converted to plugin
 identities with -identity. If OUTPUT already exists, it is not overwritten.`
 
+// Version can be set at link time to override debug.BuildInfo.Main.Version when
+// building manually without git history. It should look like "v1.2.3".
+var Version string
+
 func main() {
 	log.SetFlags(0)
 
 	p, err := plugin.New("pq")
 	if err != nil {
-		log.Fatal(err)
+		errorf("failed to create plugin: %v", err)
 	}
 	p.RegisterFlags(nil)
 
@@ -50,11 +54,10 @@ func main() {
 	flag.Parse()
 
 	if versionFlag {
-		if buildInfo, ok := debug.ReadBuildInfo(); ok {
-			fmt.Println(buildInfo.Main.Version)
-			return
+		if buildInfo, ok := debug.ReadBuildInfo(); ok && Version == "" {
+			Version = buildInfo.Main.Version
 		}
-		fmt.Println("(unknown)")
+		fmt.Println(Version)
 		return
 	}
 

extra/age-plugin-tag/plugin-tag.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"runtime/debug"
 
 	"filippo.io/age"
 	"filippo.io/age/plugin"
@@ -18,6 +19,10 @@ support to any version and implementation of age that supports plugins.
 Usually, tagged recipients are the public side of private keys held in hardware,
 where the identity side is handled by a different plugin.`
 
+// Version can be set at link time to override debug.BuildInfo.Main.Version when
+// building manually without git history. It should look like "v1.2.3".
+var Version string
+
 func main() {
 	flag.Usage = func() { fmt.Fprintf(os.Stderr, "%s\n", usage) }
 
@@ -25,8 +30,22 @@ func main() {
 	if err != nil {
 		log.Fatal(err)
 	}
+	p.RegisterFlags(nil)
+
+	versionFlag := flag.Bool("version", false, "print the version")
+	flag.Parse()
+
+	if *versionFlag {
+		if buildInfo, ok := debug.ReadBuildInfo(); ok && Version == "" {
+			Version = buildInfo.Main.Version
+		}
+		fmt.Println(Version)
+		return
+	}
+
 	p.HandleRecipient(func(b []byte) (age.Recipient, error) {
 		return tag.NewClassicRecipient(b)
 	})
+
 	os.Exit(p.Main())
 }

extra/age-plugin-tagpq/plugin-tagpq.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"runtime/debug"
 
 	"filippo.io/age"
 	"filippo.io/age/plugin"
@@ -19,6 +20,10 @@ implementation of age that supports plugins.
 Usually, tagged recipients are the public side of private keys held in hardware,
 where the identity side is handled by a different plugin.`
 
+// Version can be set at link time to override debug.BuildInfo.Main.Version when
+// building manually without git history. It should look like "v1.2.3".
+var Version string
+
 func main() {
 	flag.Usage = func() { fmt.Fprintf(os.Stderr, "%s\n", usage) }
 
@@ -26,8 +31,22 @@ func main() {
 	if err != nil {
 		log.Fatal(err)
 	}
+	p.RegisterFlags(nil)
+
+	versionFlag := flag.Bool("version", false, "print the version")
+	flag.Parse()
+
+	if *versionFlag {
+		if buildInfo, ok := debug.ReadBuildInfo(); ok && Version == "" {
+			Version = buildInfo.Main.Version
+		}
+		fmt.Println(Version)
+		return
+	}
+
 	p.HandleRecipient(func(b []byte) (age.Recipient, error) {
 		return tag.NewHybridRecipient(b)
 	})
+
 	os.Exit(p.Main())
 }