brew autoupdate runs on brew install --help

[skycaptain]

TL;DR: brew install --help calls autoupdate

And now to the long story. I was surprised by the update of readline 7; i.e. it crashed other packages I'm using on a daily basis. Therefore, the easiest way seamed to revert to an older commit and pin readline. Searching for the command on how to disable the autoupdate triggered by brew install (Since this would checkout the master again) I called brew install --help. Sadly this command also triggered the autoupdate.
I know that this is a rare scenario and this behavior may also be by design but for me this is inconvenient.

[zmwangx]

brew install --help triggering autoupdate should be considered a bug IMO. Sorry for the inconvenience.

FYI to disable autoupdate you set the HOMEBREW_NO_AUTO_UPDATE environment variable.

Also, if you haven't cleaned up your old readline yet, you can

brew switch readline 6.3.8

but you'll also need to switch whatever that has been upgraded and linked to readline 7.

[skycaptain]

Already solved the issues regarding readline using HOMEBREW_NO_AUTO_UPDATE. Was difficult though, since brew install doesn't allow pinned formulas. But installing readline 6 and 7 side by side and using brew switch finally solved everything. Anyway, thanks for your help.