Improve the "Source mismatch" error message
When /etc/crypttab gives a source device that does not match the current source, cryptsetup outputs an error message something like this:
cryptsetup: ERROR: p4-crypt: Source mismatch
This error message could include more information to make it easier to identify the problem with the crypttab entry. This patch enhances the message to look like this:
cryptsetup: ERROR: Source mismatch: p4-crypt uses 8:4, but /dev/sda1 is 8:1