Derrick Stolee <stolee@xxxxxxxxx> writes:
> The index extension documentation doesn't appear to be clear about
> which extensions are optional or required, but it seems the
> split-index is the only "required" one and uses lowercase for its
> extension id.
read-cache.c::
/* Index extensions.
*
* The first letter should be 'A'..'Z' for extensions that are not
* necessary for a correct operation (i.e. optimization data).
* When new extensions are added that _needs_ to be understood in
* order to correctly interpret the index file, pick character that
* is outside the range, to cause the reader to abort.
*/
