Add version command to slsa-provenance cli

Makefile

@@ -1,6 +1,23 @@
+GIT_TAG ?= dirty-tag
+GIT_VERSION ?= $(shell git describe --tags --always --dirty)
+GIT_HASH ?= $(shell git rev-parse HEAD)
+DATE_FMT = +'%Y-%m-%dT%H:%M:%SZ'
+SOURCE_DATE_EPOCH ?= $(shell git log -1 --pretty=%ct)
+ifdef SOURCE_DATE_EPOCH
+    BUILD_DATE ?= $(shell date -u -d "@$(SOURCE_DATE_EPOCH)" "$(DATE_FMT)" 2>/dev/null || date -u -r "$(SOURCE_DATE_EPOCH)" "$(DATE_FMT)" 2>/dev/null || date -u "$(DATE_FMT)")
+else
+    BUILD_DATE ?= $(shell date "$(DATE_FMT)")
+endif
+GIT_TREESTATE = "clean"
+DIFF = $(shell git diff --quiet >/dev/null 2>&1; if [ $$? -eq 1 ]; then echo "1"; fi)
+ifeq ($(DIFF), 1)
+    GIT_TREESTATE = "dirty"
+endif
+
 PKG=github.com/philips-labs/slsa-provenance-action/cmd/slsa-provenance/cli
+LDFLAGS="-X $(PKG).GitVersion=$(GIT_VERSION) -X $(PKG).gitCommit=$(GIT_HASH) -X $(PKG).gitTreeState=$(GIT_TREESTATE) -X $(PKG).buildDate=$(BUILD_DATE)"
 
-GO_BUILD_FLAGS := -trimpath
+GO_BUILD_FLAGS := -trimpath -ldflags $(LDFLAGS)
 COMMANDS       := slsa-provenance
 
 .PHONY: help

cmd/slsa-provenance/cli/version.go

@@ -0,0 +1,106 @@
+package cli
+
+import (
+	"context"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"runtime"
+	"strings"
+	"text/tabwriter"
+
+	"github.com/peterbourgon/ff/v3/ffcli"
+	"github.com/pkg/errors"
+)
+
+// Base version information.
+//
+// This is the fallback data used when version information from git is not
+// provided via go ldflags (e.g. via Makefile).
+var (
+	// Output of "git describe". The prerequisite is that the branch should be
+	// tagged using the correct versioning strategy.
+	GitVersion string = "devel"
+	// SHA1 from git, output of $(git rev-parse HEAD)
+	gitCommit = "unknown"
+	// State of git tree, either "clean" or "dirty"
+	gitTreeState = "unknown"
+	// Build date in ISO8601 format, output of $(date -u +'%Y-%m-%dT%H:%M:%SZ')
+	buildDate = "unknown"
+)
+
+func Version() *ffcli.Command {
+	var (
+		flagset = flag.NewFlagSet("slsa-provenance version", flag.ExitOnError)
+		outJSON = flagset.Bool("json", false, "print JSON instead of text")
+	)
+	return &ffcli.Command{
+		Name:       "version",
+		ShortUsage: "slsa-provenance version",
+		ShortHelp:  "Prints the slsa-provenance version",
+		FlagSet:    flagset,
+		Exec: func(ctx context.Context, args []string) error {
+			v := VersionInfo()
+			res := v.String()
+			if *outJSON {
+				j, err := v.JSONString()
+				if err != nil {
+					return errors.Wrap(err, "unable to generate JSON from version info")
+				}
+				res = j
+			}
+
+			fmt.Println(res)
+			return nil
+		},
+	}
+}
+
+type Info struct {
+	GitVersion   string `json:"git_version,omitempty"`
+	GitCommit    string `json:"git_commit,omitempty"`
+	GitTreeState string `json:"git_tree_state,omitempty"`
+	BuildDate    string `json:"build_date,omitempty"`
+	GoVersion    string `json:"go_version,omitempty"`
+	Compiler     string `json:"compiler,omitempty"`
+	Platform     string `json:"platform,omitempty"`
+}
+
+func VersionInfo() Info {
+	return Info{
+		GitVersion:   GitVersion,
+		GitCommit:    gitCommit,
+		GitTreeState: gitTreeState,
+		BuildDate:    buildDate,
+		GoVersion:    runtime.Version(),
+		Compiler:     runtime.Compiler,
+		Platform:     fmt.Sprintf("%s/%s", runtime.GOOS, runtime.GOARCH),
+	}
+}
+
+// String returns the string representation of the version info
+func (i *Info) String() string {
+	b := strings.Builder{}
+	w := tabwriter.NewWriter(&b, 0, 0, 2, ' ', 0)
+
+	fmt.Fprintf(w, "GitVersion:\t%s\n", i.GitVersion)
+	fmt.Fprintf(w, "GitCommit:\t%s\n", i.GitCommit)
+	fmt.Fprintf(w, "GitTreeState:\t%s\n", i.GitTreeState)
+	fmt.Fprintf(w, "BuildDate:\t%s\n", i.BuildDate)
+	fmt.Fprintf(w, "GoVersion:\t%s\n", i.GoVersion)
+	fmt.Fprintf(w, "Compiler:\t%s\n", i.Compiler)
+	fmt.Fprintf(w, "Platform:\t%s\n", i.Platform)
+
+	w.Flush()
+	return b.String()
+}
+
+// JSONString returns the JSON representation of the version info
+func (i *Info) JSONString() (string, error) {
+	b, err := json.MarshalIndent(i, "", "  ")
+	if err != nil {
+		return "", err
+	}
+
+	return string(b), nil
+}

cmd/slsa-provenance/main.go

@@ -20,10 +20,13 @@ func main() {
 		FlagSet: rootFlagSet,
 		Subcommands: []*ffcli.Command{
 			cli.Generate(),
+			cli.Version(),
 		},
 		Exec: func(ctx context.Context, args []string) error {
 			fmt.Println("slsa-provenance")
 			fmt.Println()
+
+			return cli.Version().Exec(ctx, args)
 		},
 	}