Rename msoXML to zipContains

It's a better name considering this function can be used to check any
kind of zip for headers, not only MS office files.

internal/magic/ms_office.go

@@ -46,17 +46,17 @@ var (
 
 // Xlsx matches a Microsoft Excel 2007 file.
 func Xlsx(raw []byte, limit uint32) bool {
-	return msoXML(raw, xlsxSigFiles...)
+	return zipContains(raw, xlsxSigFiles...)
 }
 
 // Docx matches a Microsoft Word 2007 file.
 func Docx(raw []byte, limit uint32) bool {
-	return msoXML(raw, docxSigFiles...)
+	return zipContains(raw, docxSigFiles...)
 }
 
 // Pptx matches a Microsoft PowerPoint 2007 file.
 func Pptx(raw []byte, limit uint32) bool {
-	return msoXML(raw, pptxSigFiles...)
+	return zipContains(raw, pptxSigFiles...)
 }
 
 // Ole matches an Open Linking and Embedding file.

internal/magic/zip.go

@@ -84,13 +84,12 @@ func (t *zipTokenizer) next() (fileName string) {
 	return string(in[fNameOffset : fNameOffset+fNameLen])
 }
 
-// msoXML reads at most first 10 local headers and returns whether the input
-// looks like a Microsoft Office file.
-func msoXML(in []byte, prefixes ...string) bool {
+// zipContains returns true if the zip file headers from in contain any of the paths.
+func zipContains(in []byte, paths ...string) bool {
 	t := zipTokenizer{in: in}
 	for i, tok := 0, t.next(); tok != ""; i, tok = i+1, t.next() {
-		for p := range prefixes {
-			if strings.HasPrefix(tok, prefixes[p]) {
+		for p := range paths {
+			if strings.HasPrefix(tok, paths[p]) {
 				return true
 			}
 		}