simple past x past perfect

[beachboy]

We finally parted, but not before he promised to show up.
We finally parted, but not before he had promised to show up.
Are both right? If yes, do they have the same meaning? And if yes, what element in this sentence enables me to use either?
Thanks

 

[Soup]

We finally parted, but not before he promised to show up.

We finally parted, but not before he had promised to show up.

Are both right?
Yes.

If yes, do they have the same meaning?
Yes.

And if yes, what element in this sentence enables me to use either?
The word before.