pkg/idtools: CanAccess(): reorder checks to allow early return

Merge the accessible() function into CanAccess, and check world-
readable permissions first, before checking owner and group.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

pkg/idtools/idtools_unix.go

@@ -90,20 +90,17 @@ func CanAccess(path string, pair Identity) bool {
 	if err != nil {
 		return false
 	}
-	fileMode := os.FileMode(statInfo.Mode())
-	permBits := fileMode.Perm()
-	return accessible(statInfo.UID() == uint32(pair.UID),
-		statInfo.GID() == uint32(pair.GID), permBits)
-}
-
-func accessible(isOwner, isGroup bool, perms os.FileMode) bool {
-	if isOwner && (perms&0100 == 0100) {
+	perms := os.FileMode(statInfo.Mode()).Perm()
+	if perms&0o001 == 0o001 {
+		// world access
 		return true
 	}
-	if isGroup && (perms&0010 == 0010) {
+	if statInfo.UID() == uint32(pair.UID) && (perms&0o100 == 0o100) {
+		// owner access.
 		return true
 	}
-	if perms&0001 == 0001 {
+	if statInfo.GID() == uint32(pair.GID) && (perms&0o010 == 0o010) {
+		// group access.
 		return true
 	}
 	return false