More comprehensive build info collection

buildinfo.go

@@ -0,0 +1,101 @@
+package main
+
+import (
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/binary"
+	"fmt"
+	"io"
+	"runtime/debug"
+	"sort"
+	"strconv"
+	"time"
+)
+
+var version = "dev" // has to be set by ldflags
+
+const (
+	buildInfoModuleStart byte = iota
+	buildInfoModuleFinish
+	buildInfoModuleDelimeter
+)
+
+func getVersion() string {
+	goVersion, date, commit, modulesChecksum, dirty := getVersionData()
+
+	dirtySuffix := ""
+	if dirty {
+		dirtySuffix = " [dirty]"
+	}
+
+	return fmt.Sprintf("%s (%s: %s on %s%s, modules checksum %s)",
+		version,
+		goVersion,
+		date.Format(time.RFC3339),
+		commit,
+		dirtySuffix,
+		modulesChecksum)
+}
+
+func getVersionData() (goVersion string, date time.Time, commit string, modulesChecksum string, dirty bool) {
+	date = time.Now()
+
+	buildInfo, ok := debug.ReadBuildInfo()
+	if !ok {
+		return
+	}
+
+	goVersion = buildInfo.GoVersion
+
+	for _, setting := range buildInfo.Settings {
+		switch setting.Key {
+		case "vcs.time":
+			date, _ = time.Parse(time.RFC3339, setting.Value)
+		case "vcs.revision":
+			commit = setting.Value
+		case "vcs.modified":
+			dirty, _ = strconv.ParseBool(setting.Value)
+		}
+	}
+
+	hasher := sha256.New()
+	if _, err := io.WriteString(hasher, buildInfo.Path); err != nil {
+		panic(err)
+	}
+	binary.Write(hasher, binary.LittleEndian, uint64(1+len(buildInfo.Deps)))
+
+	sort.Slice(buildInfo.Deps, func(i, j int) bool {
+		return buildInfo.Deps[i].Path > buildInfo.Deps[j].Path
+	})
+
+	buildInfoCheckSumModule(hasher, &buildInfo.Main)
+	for _, module := range buildInfo.Deps {
+		buildInfoCheckSumModule(hasher, module)
+	}
+
+	modulesChecksum = base64.StdEncoding.EncodeToString(hasher.Sum(nil))
+
+	return
+}
+
+func buildInfoCheckSumModule(w io.Writer, module *debug.Module) {
+	w.Write([]byte{buildInfoModuleStart})
+
+	if _, err := io.WriteString(w, module.Path); err != nil {
+		panic(err)
+	}
+
+	w.Write([]byte{buildInfoModuleDelimeter})
+
+	if _, err := io.WriteString(w, module.Version); err != nil {
+		panic(err)
+	}
+
+	w.Write([]byte{buildInfoModuleDelimeter})
+
+	if _, err := io.WriteString(w, module.Sum); err != nil {
+		panic(err)
+	}
+
+	w.Write([]byte{buildInfoModuleFinish})
+}