add support for build tag to allow to disable some features

The following build tags are available:

- "nogcs", disable Google Cloud Storage backend
- "nos3", disable S3 Compabible Object Storage backends
- "nobolt", disable Bolt data provider
- "nomysql", disable MySQL data provider
- "nopgsql", disable PostgreSQL data provider
- "nosqlite", disable SQLite data provider
- "noportable", disable portable mode

utils/version.go

@@ -1,5 +1,7 @@
 package utils
 
+import "strings"
+
 const version = "0.9.6-dev"
 
 var (
@@ -10,21 +12,34 @@ var (
 
 // VersionInfo defines version details
 type VersionInfo struct {
-	Version    string `json:"version"`
-	BuildDate  string `json:"build_date"`
-	CommitHash string `json:"commit_hash"`
+	Version    string   `json:"version"`
+	BuildDate  string   `json:"build_date"`
+	CommitHash string   `json:"commit_hash"`
+	Features   []string `json:"features"`
 }
 
 // GetVersionAsString returns the string representation of the VersionInfo struct
 func (v *VersionInfo) GetVersionAsString() string {
-	versionString := v.Version
+	var sb strings.Builder
+	sb.WriteString(v.Version)
 	if len(v.CommitHash) > 0 {
-		versionString += "-" + v.CommitHash
+		sb.WriteString("-")
+		sb.WriteString(v.CommitHash)
 	}
 	if len(v.BuildDate) > 0 {
-		versionString += "-" + v.BuildDate
+		sb.WriteString("-")
+		sb.WriteString(v.BuildDate)
 	}
-	return versionString
+	if len(v.Features) > 0 {
+		sb.WriteString(" ")
+		sb.WriteString(strings.Join(v.Features, " "))
+	}
+	return sb.String()
+}
+
+// AddFeature adds a feature description
+func AddFeature(feature string) {
+	versionInfo.Features = append(versionInfo.Features, feature)
 }
 
 func init() {