I have been using diff to compare directories on two SSDs on my laptop, tying up two USB ports and immobilising the computer for about two days.
I've reviewed its options, and don't see a better way of using it.
The man page is a bit short on detail about what it considers same/different, bu I see that I can choose weather filename case matters, whether changes in white space matter, whether fit matters when something has been changed from lower to upper case, etc.
I propose another option, a GNU extension if you like.
--ignore-contents
If filenames are the same, subject to other choices, if the file sizes are the same, if the *times match, then consider them the same. Essentially, we're only comparing the file descriptions, not their contents.
I'm ambivalent about dates, perhaps those can be user-choice too, I can think of a few reasons they might differ. Copy to/from DOS-family filesystems and NTFS or ext4 etc. Transfer between computers in different time zones or the transfer program doesn't preserve timestamps.
With this change, instead of running almost two days and finding no consequential differences, it could have been all over in a couple of minutes.
Thank you for your time and consideration.
John Summerfield
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