version: use package-level variables for linker flag support

The build ID wasn't properly being set by linker flags because struct
fields cannot be directly modified by the Go linker flags; only
package-level variables can be modified by the Go linker flags.

This change:

- Moves version information to package-level variables
- Updates initialization to use these variables
- Improves fallback mechanism to check for `vcs.revision` first
- Maintains backward compatibility with `gitrevision`

This addresses issue #3986 where the build ID was displaying a hardcoded
hash instead of the proper git commit hash or custom value.

Note: I could not determine why `gitrevision` was being used but it may
have been from historical linker flag usage, such as
`-ldflags "-X main.gitrevision=$(git rev-parse HEAD)"`. Since Go 1.18
`vcs.revision` is the standard now. I have maintained the `gitrevision`
look for backwards compatibility.

Fixes #3986

Author: codeaucafe

pkg/version/fixbuild.go

@@ -9,14 +9,27 @@ func init() {
 }
 
 func buildInfoFixBuild(v *Version) {
+	if v.Build != "$Id$" {
+		return
+	}
+
 	info, ok := debug.ReadBuildInfo()
 	if !ok {
 		return
 	}
-	for i := range info.Settings {
-		if info.Settings[i].Key == "gitrevision" {
-			v.Build = info.Settings[i].Value
-			break
+
+	for _, setting := range info.Settings {
+		if setting.Key == "vcs.revision" {
+			v.Build = setting.Value
+			return
+		}
+	}
+
+	// If we didn't find vcs.revision, try the old key for backward compatibility
+	for _, setting := range info.Settings {
+		if setting.Key == "gitrevision" {
+			v.Build = setting.Value
+			return
 		}
 	}
 }

pkg/version/version.go

@@ -5,6 +5,15 @@ import (
 	"runtime"
 )
 
+// Package-level variables that can be set by linker flags
+var (
+	VersionMajor    = "1"
+	VersionMinor    = "24"
+	VersionPatch    = "2"
+	VersionMetadata = ""
+	BuildVersion    = "$Id$"
+)
+
 // Version represents the current version of Delve.
 type Version struct {
 	Major    string
@@ -16,8 +25,11 @@ type Version struct {
 
 // DelveVersion is the current version of Delve.
 var DelveVersion = Version{
-	Major: "1", Minor: "24", Patch: "2", Metadata: "",
-	Build: "$Id$",
+	Major:    VersionMajor,
+	Minor:    VersionMinor,
+	Patch:    VersionPatch,
+	Metadata: VersionMetadata,
+	Build:    BuildVersion,
 }
 
 func (v Version) String() string {