add ReplaceExtensions to pathtools

Change-Id: I6dc92323d4b0ef4b0f31076c868802dc568346c4

blueprint/pathtools/lists.go

@@ -2,6 +2,11 @@ package pathtools
 
 import (
 	"path/filepath"
+	"regexp"
+)
+
+var (
+	replaceRegexp = regexp.MustCompile(`\.[^\.]+$`)
 )
 
 // PrefixPaths returns a list of paths consisting of prefix joined with each
@@ -14,3 +19,11 @@ func PrefixPaths(paths []string, prefix string) []string {
 	}
 	return result
 }
+
+func ReplaceExtensions(paths []string, extension string) []string {
+	result := make([]string, len(paths))
+	for i, path := range paths {
+		result[i] = replaceRegexp.ReplaceAllString(path, "."+extension)
+	}
+	return result
+}