pkg/archive: strip "write" bits again on Windows

1. Commit 1a22418f9f changed permissions to `0700`
   on Windows, or more factually, it removed `rw` (`chmod g-rw,o-rw`) and added
   executable bits (`chmod u+x`).
2. This was too restrictive, and b7dc9040f0 changed
   permissions to only remove the group- and world-writable bits to give read and
  execute access to everyone, but setting execute permissions for everyone.
3. However, this also removed the non-permission bits, so 41eb61d5c2
   updated the code to preserve those, and keep parity with Linux.

This changes it back to `2.`. I wonder (_think_) _permission_ bits (read, write)
can be portable, except for the _executable_ bit (which is not present on Windows).
The alternative could be to keep the permission bits, and only set the executable
bit (`perm | 0111`) for everyone (equivalent of `chmod +x`), but that likely would
be a breaking change.

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

pkg/archive/archive_windows.go

@@ -31,8 +31,11 @@ func CanonicalTarNameForPath(p string) string {
 // chmodTarEntry is used to adjust the file permissions used in tar header based
 // on the platform the archival is done.
 func chmodTarEntry(perm os.FileMode) os.FileMode {
+	// Remove group- and world-writable bits.
+	perm &= 0o755
+
 	// Add the x bit: make everything +x on Windows
-	return perm | 0111
+	return perm | 0o111
 }
 
 func setHeaderForSpecialDevice(hdr *tar.Header, name string, stat interface{}) (err error) {

pkg/archive/archive_windows_test.go

@@ -71,7 +71,7 @@ func TestChmodTarEntry(t *testing.T) {
 		in, expected os.FileMode
 	}{
 		{0000, 0111},
-		{0777, 0777},
+		{0777, 0755},
 		{0644, 0755},
 		{0755, 0755},
 		{0444, 0555},