Move to setting version info explicitly in linker flags

We don't have go built-in VCS information in a nix build because the git
repository isn't present. After struggling to build an overlay that
would provide it, I decided this path is easier of just injecting in the
data that we need.

Issue: #5

version/version.go

@@ -1,65 +1,11 @@
 package version
 
 import (
-	"runtime/debug"
-	"strconv"
 	"time"
 )
 
-// These will be set by ldflags at build time
-var (
-	Version    = "dev"
-	Commit     = ""
-	BuildTime  = "0"
-	IsModified = "false"
-)
-
 type VersionInfo struct {
 	BuildTime  time.Time `json:"build_time"`
 	IsModified bool      `json:"is_modified"`
 	Revision   string    `json:"revision"`
 }
-
-func Get() VersionInfo {
-	// Try ldflags first (set by Nix build)
-	if Commit != "" && Commit != "unknown" {
-		var buildTime time.Time
-		if timestamp, err := strconv.ParseInt(BuildTime, 10, 64); err == nil && timestamp > 0 {
-			buildTime = time.Unix(timestamp, 0)
-		}
-
-		return VersionInfo{
-			Revision:   Commit,
-			BuildTime:  buildTime,
-			IsModified: IsModified == "true",
-		}
-	}
-
-	// Fallback to debug.ReadBuildInfo() for development
-	info, ok := debug.ReadBuildInfo()
-	if !ok {
-		return VersionInfo{
-			Revision: "unknown",
-		}
-	}
-
-	var version VersionInfo
-	for _, setting := range info.Settings {
-		switch setting.Key {
-		case "vcs.modified":
-			version.IsModified = setting.Value == "true"
-		case "vcs.revision":
-			if len(setting.Value) > 7 {
-				version.Revision = setting.Value[:7]
-			} else {
-				version.Revision = setting.Value
-			}
-		case "vcs.time":
-			if t, err := time.Parse(time.RFC3339, setting.Value); err == nil {
-				version.BuildTime = t
-			}
-		}
-	}
-
-	return version
-}