Added version command and corresponding implementation

internal/version.go

@@ -0,0 +1,42 @@
+package magellan
+
+import (
+	"fmt"
+	"os/exec"
+	"strings"
+)
+
+// VersionCommit() returns a string with 'r{commit_count}.{commit_version}' format.
+func VersionCommit() string {
+	var (
+		version  string
+		revlist  []byte
+		revparse []byte
+		err      error
+	)
+	revlist, err = exec.Command("git", "rev-list", "--count", "HEAD").Output()
+	if err != nil {
+		return ""
+	}
+
+	revparse, err = exec.Command("git", "rev-parse", "--short", "HEAD").Output()
+	if err != nil {
+		return ""
+	}
+	version = fmt.Sprintf("r%s.%s", strings.TrimRight(string(revlist), "\n"), string(revparse))
+	return strings.TrimRight(version, "\n")
+}
+
+// VersionTag() returns  a string with format '{git_tag}' using the `git describe` command.
+func VersionTag() string {
+	var (
+		describe []byte
+		err      error
+	)
+	describe, err = exec.Command("git", "describe", "--long", "HEAD").Output()
+	if err != nil {
+		return ""
+	}
+
+	return strings.TrimRight(string(describe), "\n")
+}