I have a backup of a GMail account which creates folders by year, month, date and within them .eml files for each email.
I'm migrating to a different GMail account so I'm moving the emails to the new account, and I have a backup also of the second account.
So it's something like: Account1/2022/5/1/aaaa.eml and Account2/2022/5/1/bbbb.eml .. with each being identical emails (a diff of the two files will confirm that).
Of course I don't just have 1 email. I have about 200,000, and the number of files in the two backups is slightly different so I want to find the discrepancies.
So: Any suggestions? I could run a standard dedup program but that'll be very slow given that it'll be comparing 200k files with another 200k files. In most cases I suspect the missing file(s) will stand out just from their file sizes on a per-directory comparison.