bug: "C-x z" ("repeat") no longer works correctly with M-x

[Miles Bader]

It used to be (up until fairly recently, dunno the exact point at
which it changed) that "C-x z" would correctly repeat the previous
extended command; e.g. if you entered "M-x pwd RET", and then "C-x z",
the latter would re-invoke "pwd".  This was very useful.

Now it no longer does this -- instead it just repeats "M-x", prompting
for a command.  This is obviously far less useful behavior...

Thanks,

-Miles

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