1 files changed, 94 insertions, 0 deletions
diff --git a/version.go b/version.go
new file mode 100644
index 000000000..de9bd8753
--- /dev/null
+++ b/version.go
@@ -0,0 +1,94 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"runtime/debug"
+	"strings"
+
+	"github.com/git-bug/git-bug/commands"
+	"golang.org/x/mod/semver"
+)
+
+var (
+	version = "undefined"
+)
+
+// getVersion returns a string representing the version information defined when
+// the binary was built, or a sane default indicating a local build. a string is
+// always returned. an error may be returned along with the string in the event
+// that we detect a local build but are unable to get build metadata.
+//
+// TODO: support validation of the version (that it's a real version)
+// TODO: support notifying the user if their version is out of date
+func getVersion() (string, error) {
+	var arch string
+	var commit string
+	var modified bool
+	var platform string
+
+	var v strings.Builder
+
+	// this supports overriding the default version if the deprecated var used
+	// for setting the exact version for releases is supplied. we are doing this
+	// in order to give downstream package maintainers a longer window to
+	// migrate.
+	//
+	// TODO: 0.12.0: remove support for old build tags
+	if version == "undefined" && commands.GitExactTag != "" {
+		version = commands.GitExactTag
+	}
+
+	// automatically add the v prefix if it's missing
+	if version != "undefined" && !strings.HasPrefix(version, "v") {
+		version = fmt.Sprintf("v%s", version)
+	}
+
+	// reset the version string to undefined if it is invalid
+	if ok := semver.IsValid(version); !ok {
+		version = "undefined"
+	}
+
+	v.WriteString(version)
+
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		v.WriteString(fmt.Sprintf(" (no build info)\n"))
+		return v.String(), errors.New("unable to read build metadata")
+	}
+
+	for _, kv := range info.Settings {
+		switch kv.Key {
+		case "GOOS":
+			platform = kv.Value
+		case "GOARCH":
+			arch = kv.Value
+		case "vcs.modified":
+			if kv.Value == "true" {
+				modified = true
+			}
+		case "vcs.revision":
+			commit = kv.Value
+		}
+	}
+
+	if commit != "" {
+		v.WriteString(fmt.Sprintf(" %.12s", commit))
+	}
+
+	if modified {
+		v.WriteString("/dirty")
+	}
+
+	v.WriteString(fmt.Sprintf(" %s", info.GoVersion))
+
+	if platform != "" {
+		v.WriteString(fmt.Sprintf(" %s", platform))
+	}
+
+	if arch != "" {
+		v.WriteString(fmt.Sprintf(" %s", arch))
+	}
+
+	return fmt.Sprint(v.String(), "\n"), nil
+}