rebase question

I want to rebase the current branch B1 from origin/A1 to origin/A2 so I want to use this command git --onto origin/A2 origin/A1 B1

Q1: is this command right? (A2 is based on A1, current branch is B1,
B1 is already pushed to origin, a remote repo, and I think I will
force push B1 after rebase)

but I accidentally typed
 git --onto origin/A2 origin/A1 origin/A2
and git says
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First, rewinding head to replay your work on top of it...
Fast-forwarded origin/base to origin/base.
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Q2:I assume this command is safe and it didn't change anything right?

THANKS IN ADVANCE