internal/version: use gitCommit injection in version handling code (#25851)

This changes the CI build to store the git commit and date into package
internal/version instead of package main. Doing this essentially merges our
two ways of tracking the go-ethereum version into a single place, achieving
two objectives:

- Bad block reports, which use version.Info(), will now have the git commit
  information even when geth is built in an environment such as
  launchpad.net where git access is unavailable.

- For geth builds created by `go build ./cmd/geth` (i.e. not using `go run
  build/ci.go install`), git information stored by the go tool is now used
  in the p2p node name as well as in `geth version` and `geth
  version-check`.

internal/flags/helpers.go

@@ -20,15 +20,17 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/ethereum/go-ethereum/internal/version"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/urfave/cli/v2"
 )
 
 // NewApp creates an app with sane defaults.
-func NewApp(gitCommit, gitDate, usage string) *cli.App {
+func NewApp(usage string) *cli.App {
+	git, _ := version.VCS()
 	app := cli.NewApp()
 	app.EnableBashCompletion = true
-	app.Version = params.VersionWithCommit(gitCommit, gitDate)
+	app.Version = params.VersionWithCommit(git.Commit, git.Date)
 	app.Usage = usage
 	app.Copyright = "Copyright 2013-2022 The go-ethereum Authors"
 	app.Before = func(ctx *cli.Context) error {

internal/version/vcs_fallback.go

@@ -23,6 +23,6 @@ import "runtime/debug"
 
 // In Go versions before 1.18, VCS information is not available.
 
-func vcsInfo(info *debug.BuildInfo) (gitStatus, bool) {
-	return gitStatus{}, false
+func buildInfoVCS(info *debug.BuildInfo) (VCSInfo, bool) {
+	return VCSInfo{}, false
 }

internal/version/vcs_go1.18.go

@@ -19,29 +19,36 @@
 
 package version
 
-import "runtime/debug"
+import (
+	"runtime/debug"
+	"time"
+)
 
 // In go 1.18 and beyond, the go tool embeds VCS information into the build.
 
-// vcsInfo returns VCS information of the build.
-func vcsInfo(info *debug.BuildInfo) (s gitStatus, ok bool) {
+const (
+	govcsTimeLayout = "2006-01-02T15:04:05Z"
+	ourTimeLayout   = "20060102"
+)
+
+// buildInfoVCS returns VCS information of the build.
+func buildInfoVCS(info *debug.BuildInfo) (s VCSInfo, ok bool) {
 	for _, v := range info.Settings {
 		switch v.Key {
 		case "vcs.revision":
-			if len(v.Value) < 8 {
-				s.revision = v.Value
-			} else {
-				s.revision = v.Value[:8]
-			}
+			s.Commit = v.Value
 		case "vcs.modified":
 			if v.Value == "true" {
-				s.modified = true
+				s.Dirty = true
 			}
 		case "vcs.time":
-			s.time = v.Value
+			t, err := time.Parse(govcsTimeLayout, v.Value)
+			if err == nil {
+				s.Date = t.Format(ourTimeLayout)
+			}
 		}
 	}
-	if s.revision != "" && s.time != "" {
+	if s.Commit != "" && s.Date != "" {
 		ok = true
 	}
 	return

internal/version/version.go

@@ -19,6 +19,7 @@ package version
 
 import (
 	"fmt"
+	"runtime"
 	"runtime/debug"
 	"strings"
 
@@ -27,6 +28,43 @@ import (
 
 const ourPath = "github.com/ethereum/go-ethereum" // Path to our module
 
+// These variables are set at build-time by the linker when the build is
+// done by build/ci.go.
+var gitCommit, gitDate string
+
+// VCSInfo represents the git repository state.
+type VCSInfo struct {
+	Commit string // head commit hash
+	Date   string // commit time in YYYYMMDD format
+	Dirty  bool
+}
+
+// VCS returns version control information of the current executable.
+func VCS() (VCSInfo, bool) {
+	if gitCommit != "" {
+		// Use information set by the build script if present.
+		return VCSInfo{Commit: gitCommit, Date: gitDate}, true
+	}
+	if buildInfo, ok := debug.ReadBuildInfo(); ok {
+		if buildInfo.Main.Path == ourPath {
+			return buildInfoVCS(buildInfo)
+		}
+	}
+	return VCSInfo{}, false
+}
+
+// ClientName creates a software name/version identifier according to common
+// conventions in the Ethereum p2p network.
+func ClientName(clientIdentifier string) string {
+	git, _ := VCS()
+	return fmt.Sprintf("%s/v%v/%v-%v/%v",
+		strings.Title(clientIdentifier),
+		params.VersionWithCommit(git.Commit, git.Date),
+		runtime.GOOS, runtime.GOARCH,
+		runtime.Version(),
+	)
+}
+
 // runtimeInfo returns build and platform information about the current binary.
 //
 // If the package that is currently executing is a prefixed by our go-ethereum
@@ -40,22 +78,20 @@ func Info() (version, vcs string) {
 		return version, ""
 	}
 	version = versionInfo(buildInfo)
-	if status, ok := vcsInfo(buildInfo); ok {
+	if status, ok := VCS(); ok {
 		modified := ""
-		if status.modified {
+		if status.Dirty {
 			modified = " (dirty)"
 		}
-		vcs = status.revision + "-" + status.time + modified
+		commit := status.Commit
+		if len(commit) > 8 {
+			commit = commit[:8]
+		}
+		vcs = commit + "-" + status.Date + modified
 	}
 	return version, vcs
 }
 
-type gitStatus struct {
-	revision string
-	time     string
-	modified bool
-}
-
 // versionInfo returns version information for the currently executing
 // implementation.
 //