add version info to the binary

Makefile

@@ -2,19 +2,24 @@ GODEPS = $(shell git ls-files '*.go' go.mod go.sum)
 GOBIN = $(shell go env GOPATH)/bin/
 
 GOOSARCHS = $(sort \
-				linux/amd64 \
-				linux/arm64 \
-				darwin/amd64 \
-				darwin/arm64 \
-				windows/amd64/.exe \
-			)
+			darwin/amd64 \
+			darwin/arm64 \
+			linux/amd64 \
+			linux/arm64 \
+			windows/amd64/.exe \
+			windows/arm64/.exe)
 
-VERSION = $(shell git describe --dirty)
-LDFLAGS = -ldflags "-X main.Version=$(VERSION)"
+VSN = $(shell git describe --dirty)
+VSNHASH = $(shell git rev-parse --verify HEAD)
+LDFLAGS = -ldflags "-X main.Version=$(VSN) -X main.VersionHash=$(VSNHASH)"
+
+.PHONY: test
+test:
+	go test -race -cover ./...
 
 define undockertarget
-UNDOCKERS += undocker-$(1)-$(2)-$(VERSION)-$(firstword $(3))
-undocker-$(1)-$(2)-$(VERSION)$(firstword $(3)): $(GODEPS)
+UNDOCKERS += undocker-$(1)-$(2)-$(VSN)$(firstword $(3))
+undocker-$(1)-$(2)-$(VSN)$(firstword $(3)): $(GODEPS)
 	CGO_ENABLED=0 GOOS=$(1) GOARCH=$(2) go build $(LDFLAGS) -o $$@
 endef
 
@@ -22,11 +27,7 @@ $(foreach goosarch,$(GOOSARCHS),\
 	$(eval $(call undockertarget,$(word 1,$(subst /, ,$(goosarch))),$(word 2,$(subst /, ,$(goosarch))),$(word 3,$(subst /, ,$(goosarch))))))
 
 .PHONY: all
-all: $(UNDOCKERS) coverage.html
-
-.PHONY: test
-test:
-	go test -race -cover ./...
+all: $(UNDOCKERS)
 
 .PHONY: lint
 lint: vet staticcheck
@@ -54,4 +55,4 @@ sha256sum.txt.asc: sha256sum.txt
 
 .PHONY: clean
 clean:
-	rm -f $(UNDOCKERS) coverage.html sha256sum.txt sha256sum.txt.asc
+	rm -f undocker-*-v* coverage.html sha256sum.txt sha256sum.txt.asc

README.md

@@ -80,11 +80,7 @@ Similar Projects
 Changelog
 ---------
 
-**1.0.1**
-
-* bugfix: add missing error check when opening the tarball.
-
-**1.0**
+**v1.0**
 
 * initial release: `rootfs.Flatten` and a simple command-line application.
 

main.go

@@ -11,6 +11,9 @@ import (
 	"git.sr.ht/~motiejus/undocker/rootfs"
 )
 
+var Version = "unknown"
+var VersionHash = "unknown"
+
 const _usage = `Usage:
   %s <infile> <outfile>
 
@@ -19,13 +22,21 @@ Flatten a Docker container image to a root file system.
 Arguments:
   <infile>:  Input Docker container. Tarball.
   <outfile>: Output tarball, the root file system. '-' is stdout.
+
+undocker %s (%s)
+Built with %s
 `
 
 func main() {
 	runtime.GOMAXPROCS(1) // no need to create that many threads
 
 	if len(os.Args) != 3 {
-		fmt.Fprintf(os.Stderr, _usage, filepath.Base(os.Args[0]))
+		fmt.Fprintf(os.Stderr, _usage,
+			filepath.Base(os.Args[0]),
+			Version,
+			VersionHash,
+			runtime.Version(),
+		)
 		os.Exit(1)
 	}