Add more linters to improve code readability (#19989)

Add nakedret, unconvert, wastedassign, stylecheck and nolintlint linters to improve code readability

- nakedret - https://github.com/alexkohler/nakedret - nakedret is a Go static analysis tool to find naked returns in functions greater than a specified function length.
- unconvert - https://github.com/mdempsky/unconvert - Remove unnecessary type conversions
- wastedassign - https://github.com/sanposhiho/wastedassign -  wastedassign finds wasted assignment statements.
- notlintlint -  Reports ill-formed or insufficient nolint directives
- stylecheck - https://staticcheck.io/docs/checks/#ST - keep style consistent
  - excluded: [ST1003 - Poorly chosen identifier](https://staticcheck.io/docs/checks/#ST1003) and [ST1005 - Incorrectly formatted error string](https://staticcheck.io/docs/checks/#ST1005)

services/gitdiff/gitdiff.go

@@ -1011,7 +1011,7 @@ parsingLoop:
 
 func skipToNextDiffHead(input *bufio.Reader) (line string, err error) {
 	// need to skip until the next cmdDiffHead
-	isFragment, wasFragment := false, false
+	var isFragment, wasFragment bool
 	var lineBytes []byte
 	for {
 		lineBytes, isFragment, err = input.ReadLine()
@@ -1036,7 +1036,7 @@ func skipToNextDiffHead(input *bufio.Reader) (line string, err error) {
 		}
 		line += tail
 	}
-	return
+	return line, err
 }
 
 func parseHunks(curFile *DiffFile, maxLines, maxLineCharacters int, input *bufio.Reader) (lineBytes []byte, isFragment bool, err error) {
@@ -1257,8 +1257,7 @@ func createDiffFile(diff *Diff, line string) *DiffFile {
 
 	rd := strings.NewReader(line[len(cmdDiffHead):] + " ")
 	curFile.Type = DiffFileChange
-	oldNameAmbiguity := false
-	newNameAmbiguity := false
+	var oldNameAmbiguity, newNameAmbiguity bool
 
 	curFile.OldName, oldNameAmbiguity = readFileName(rd)
 	curFile.Name, newNameAmbiguity = readFileName(rd)