add support for dest_dir_field_name (#22)

Author: tenox7

README.adoc

@@ -99,6 +99,9 @@ The default size is **1G**.
 |**create_uuid_dir**
 |If set to `true`, each file will get a unique directory with a UUID as its name.
 
+|**dest_dir_field_name**
+|If set, the dest_dir will be set from the specified form value.
+
 |===
 
 === Caddy Variables

caddyfile.go

@@ -103,6 +103,10 @@ func (u *Upload) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 					return d.Errf("parsing create_uuid_dir: %v", err)
 				}
 				u.CreateUuidDir = uuidDirBool
+			case "dest_dir_field_name":
+				if !d.Args(&u.DestDirFieldName) {
+					return d.ArgErr()
+				}
 			default:
 				return d.Errf("unrecognized servers option '%s'", d.Val())
 			}

upload.go

@@ -39,6 +39,7 @@ type Upload struct {
 	NotifyURL        string `json:"notify_url,omitempty"`
 	NotifyMethod     string `json:"notify_method,omitempty"`
 	CreateUuidDir    bool   `json:"create_uuid_dir,omitempty"`
+	DestDirFieldName string `json:"dest_dir_field_name,omitempty"`
 
 	MyTlsSetting struct {
 		InsecureSkipVerify bool   `json:"insecure,omitempty"`
@@ -66,10 +67,10 @@ func (u *Upload) Provision(ctx caddy.Context) error {
 
 	repl := caddy.NewReplacer()
 
-	if u.DestDir == "" {
+	if u.DestDir == "" && u.DestDirFieldName == "" {
 		u.logger.Error("Provision",
-			zap.String("msg", "no Destination Directory specified (dest_dir)"))
-		return fmt.Errorf("no Destination Directory specified (dest_dir)")
+			zap.String("msg", "no Destination Directory specified (dest_dir or dest_dir_field_name)"))
+		return fmt.Errorf("no Destination Directory specified (dest_dir or dest_dir_field_name)")
 	}
 
 	if u.RootDir == "" {
@@ -171,6 +172,7 @@ func (u *Upload) Provision(ctx caddy.Context) error {
 		zap.Bool("CreateUuidDir", u.CreateUuidDir),
 		zap.String("capath", u.MyTlsSetting.CAPath),
 		zap.Bool("insecure", u.MyTlsSetting.InsecureSkipVerify),
+		zap.String("dest_dir_field_name", u.DestDirFieldName),
 	)
 
 	return nil
@@ -239,6 +241,10 @@ func (u Upload) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp
 		}
 	}
 
+	if u.DestDirFieldName != "" {
+		u.DestDir = r.FormValue(u.DestDirFieldName)
+	}
+
 	concatDir := caddyhttp.SanitizedPathJoin(u.RootDir, u.DestDir)
 
 	if u.CreateUuidDir {