Is your feature request related to a problem? Please describe.
Lines that only differ in whitespace are not deduplicated out of my shell history. For example, commands cd and cd are both saved in the history despite being semantically and almost syntactically same.

Describe the solution you'd like
Enable HIST_REDUCE_BLANKS zsh option.
Docs:

HIST_REDUCE_BLANKS
Remove superfluous blanks from each command line being added to the history list.

Describe alternatives you've considered
Enabling HIST_REDUCE_BLANKS in my local configuration but I think this might be useful to many people without having any negative effects on people who don't care.

I'm wondering what everyone thinks.