tags-compression-info-list

tags-compression-info-list is a variable defined in `etags.el'.
Its value is

("" ".Z" ".bz2" ".gz" ".xz" ".tgz")

Documentation:
List of extensions tried by etags when `auto-compression-mode' is on.
An empty string means search the non-compressed file.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.