cmd: add version command

Report the build version and commit hash through both `llformat
version` and `llformat --version`.

Inject version data from the Makefile for local builds and fall
back to Go build info for module installs.

Author: bhandras

Makefile

@@ -1,6 +1,9 @@
 GO       ?= go
 BIN_DIR  ?= bin
 BIN      := $(BIN_DIR)/llformat
+VERSION  ?= $(shell git describe --tags --dirty --always 2>/dev/null || echo dev)
+COMMIT   ?= $(shell git rev-parse HEAD 2>/dev/null || echo unknown)
+LDFLAGS  ?= -X main.buildVersion=$(VERSION) -X main.buildCommit=$(COMMIT)
 
 .PHONY: all build install unit test clean
 .PHONY: fmt fmt-check lint self-check
@@ -10,13 +13,16 @@ all: build
 # Build the llformat CLI
 build: $(BIN)
 
-$(BIN): $(shell find formatter -name '*.go') $(shell find cmd -name '*.go') go.mod go.sum
+$(BIN): FORCE $(shell find formatter -name '*.go') $(shell find cmd -name '*.go') go.mod go.sum Makefile
 	@mkdir -p $(BIN_DIR)
-	$(GO) build -o $@ ./cmd/llformat
+	$(GO) build -ldflags "$(LDFLAGS)" -o $@ ./cmd/llformat
+
+.PHONY: FORCE
+FORCE:
 
 # Install llformat to GOPATH/bin
 install: build
-	$(GO) install ./cmd/llformat
+	$(GO) install -ldflags "$(LDFLAGS)" ./cmd/llformat
 
 # Run unit tests
 unit test:
@@ -38,7 +44,7 @@ fmt-check: build
 self-binary-check: build
 	@tmp=$$(mktemp -t llformat_bin.XXXXXX); \
 	cp $(BIN) $$tmp; \
-	$(GO) build -o $(BIN) ./cmd/llformat; \
+	$(GO) build -ldflags "$(LDFLAGS)" -o $(BIN) ./cmd/llformat; \
 	cmp -s $$tmp $(BIN); \
 	rm -f $$tmp; \
 	echo "Self-binary-check ok: reproducible build."

cmd/llformat/main.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"runtime/debug"
 	"sort"
 	"strings"
 
@@ -18,6 +19,7 @@ func main() {
 
 type cliFlags struct {
 	write              bool
+	version            bool
 	colLimit           int
 	tabStop            int
 	moveInline         bool
@@ -50,6 +52,10 @@ func run(args []string, stdout, stderr io.Writer) int {
 		&f.write, "write", false,
 		"write result to (source) file instead of stdout",
 	)
+	fs.BoolVar(
+		&f.version, "version", false,
+		"print version information and exit",
+	)
 	fs.IntVar(&f.colLimit, "col", 80, "column limit for formatting")
 	fs.IntVar(
 		&f.tabStop, "tab", 8, "tab stop width for column calculations",
@@ -112,6 +118,10 @@ func run(args []string, stdout, stderr io.Writer) int {
 		return 2
 	}
 
+	if f.version || isVersionCommand(fs.Args()) {
+		return runVersion(stdout)
+	}
+
 	cfg, err := buildPipelineConfig(f)
 	if err != nil {
 		fmt.Fprintln(stderr, err)
@@ -184,6 +194,7 @@ func printUsage(w io.Writer) {
 	)
 	fmt.Fprintln(w, "  llformat --print-plan")
 	fmt.Fprintln(w, "  llformat --print-logcalls-patterns")
+	fmt.Fprintln(w, "  llformat version")
 	fmt.Fprintln(w)
 	fmt.Fprintln(w, "flags:")
 	fmt.Fprintln(
@@ -236,6 +247,10 @@ func printUsage(w io.Writer) {
 		w, "  --print-logcalls-patterns print log/printf matching "+
 			"patterns and exit",
 	)
+	fmt.Fprintln(
+		w, "  --version                 print version information "+
+			"and exit",
+	)
 	fmt.Fprintln(
 		w, "  --trace-dsl               trace applied DSL edits to "+
 			"stderr",
@@ -246,6 +261,77 @@ func printUsage(w io.Writer) {
 	)
 }
 
+func isVersionCommand(args []string) bool {
+	return len(args) == 1 && args[0] == "version"
+}
+
+func runVersion(w io.Writer) int {
+	info := versionInfo()
+	fmt.Fprintf(w, "llformat version %s\n", info.Version)
+	fmt.Fprintf(w, "commit %s\n", info.Commit)
+
+	return 0
+}
+
+type versionDetails struct {
+	Version string
+	Commit  string
+}
+
+var (
+	buildVersion = ""
+	buildCommit  = ""
+)
+
+func versionInfo() versionDetails {
+	version := buildVersion
+	commit := buildCommit
+
+	if bi, ok := debug.ReadBuildInfo(); ok {
+		if version == "" && bi.Main.Version != "" &&
+			bi.Main.Version != "(devel)" {
+
+			version = bi.Main.Version
+		}
+
+		for _, setting := range bi.Settings {
+			switch setting.Key {
+			case "vcs.revision":
+				if commit == "" {
+					commit = shortCommit(setting.Value)
+				}
+
+			case "vcs.modified":
+				if setting.Value == "true" && version != "" &&
+					!strings.HasSuffix(version, "-dirty") {
+
+					version += "-dirty"
+				}
+			}
+		}
+	}
+
+	if version == "" {
+		version = "dev"
+	}
+	if commit == "" {
+		commit = "unknown"
+	}
+
+	return versionDetails{
+		Version: version,
+		Commit:  commit,
+	}
+}
+
+func shortCommit(commit string) string {
+	if len(commit) <= 12 {
+		return commit
+	}
+
+	return commit[:12]
+}
+
 func buildPipelineConfig(f cliFlags) (formatter.PipelineConfig, error) {
 	excludes := parseCommaList(f.multilineExclude)
 	logCallsNames := parseCommaList(f.logCallsNames)

cmd/llformat/main_test.go

@@ -64,3 +64,44 @@ func TestRunMultiplePathsRequireWrite(t *testing.T) {
 		"multiple paths require -w/--write",
 	)
 }
+
+func TestRunVersionCommand(t *testing.T) {
+	oldVersion, oldCommit := buildVersion, buildCommit
+	buildVersion, buildCommit = "v1.2.3-test", "abcdef123456"
+	t.Cleanup(func() {
+		buildVersion, buildCommit = oldVersion, oldCommit
+	})
+
+	var stdout, stderr bytes.Buffer
+	code := run([]string{"version"}, &stdout, &stderr)
+
+	require.Equal(t, 0, code)
+	require.Empty(t, stderr.String())
+	require.Equal(
+		t, "llformat version v1.2.3-test\ncommit abcdef123456\n",
+		stdout.String(),
+	)
+}
+
+func TestRunVersionFlag(t *testing.T) {
+	oldVersion, oldCommit := buildVersion, buildCommit
+	buildVersion, buildCommit = "v1.2.3-test", "abcdef123456"
+	t.Cleanup(func() {
+		buildVersion, buildCommit = oldVersion, oldCommit
+	})
+
+	var stdout, stderr bytes.Buffer
+	code := run([]string{"--version"}, &stdout, &stderr)
+
+	require.Equal(t, 0, code)
+	require.Empty(t, stderr.String())
+	require.Equal(
+		t, "llformat version v1.2.3-test\ncommit abcdef123456\n",
+		stdout.String(),
+	)
+}
+
+func TestShortCommit(t *testing.T) {
+	require.Equal(t, "abcdef123456", shortCommit("abcdef1234567890"))
+	require.Equal(t, "abc", shortCommit("abc"))
+}