support exclude filter

README.md

@@ -67,5 +67,5 @@ There are two main commands: `PopulateTree` to prepare source (format, add metad
 Also both commands use `Config` object that can be prepared by `NewConfig` command. With it can be configurable readable formats, attachment directory, custom meta and excludes (not movable files by regexp).
 
 `Tree` object has methods: `FileById` to get `File` by Id, `Slice` to get sub-tree of given path and `Filter` to filter tree by filter.
-Filter contains array of meta key and searching value. `tag` key is searched as equal and other meta values of keys can contain part.
+Filter contains array of meta key and searching value. `tag` key is searched as equal and other meta values of keys can contain part. If `-` is before key - filter is filter out.
 

tree.go

@@ -79,9 +79,16 @@ func (t Tree) Filter(filter map[string][]string) (Tree, bool) {
 
 	for _, f := range t.Files {
 		addFile := false
+		exclude := false
 		for option, values := range filter {
+			negative := false
+			if string(option[0]) == "-" {
+				negative = true
+				option = option[1:]
+			}
+
 			for _, value := range values {
-				if option == "tag" {
+				if !negative && option == "tag" {
 					for _, tag := range f.Tags {
 						if tag == value {
 							addFile = true
@@ -89,12 +96,24 @@ func (t Tree) Filter(filter map[string][]string) (Tree, bool) {
 					}
 					continue
 				}
-				if strings.Contains(f.Meta[option], value) {
+				if negative && option == "tag" {
+					for _, tag := range f.Tags {
+						if tag == value {
+							exclude = true
+						}
+					}
+					continue
+				}
+				if !negative && strings.Contains(f.Meta[option], value) {
 					addFile = true
+					continue
+				}
+				if negative && strings.Contains(f.Meta[option], value) {
+					exclude = true
 				}
 			}
 		}
-		if addFile {
+		if addFile && !exclude {
 			found = true
 			filtered.Files = append(filtered.Files, f)
 		}