Comment # 16 on bug 1093836 from Manfred Hollstein

This is getting more and more complex. According to what we have found out so
far, I had assumed that the following should work, but it doesn't:

0. This is all on openSUSE Leap 42.3 using gpg2-2.0:
1. Export all my private keys (I have two different ones) as ascii armored
files
     gpg2 -a --export-secret-key "$key" > "$key"-secret-gpg.key.asc
2. Export all the public keys I have a trust relationship with
     gpg2 -a --export "$key" > "$key"-public-gpg.key.asc
3. Export the owner trustdb
     gpg2 --export-ownertrust > ownertrust-gpg.txt
4. Log out to terminate all processes potentially using ~/.gnupg
5. Run the following in some vt as normal user "manfred":
     mkdir -p ~/.OS/os42.3/.gnupg/.backup; chmod 700 ~/.OS/os42.3/.gnupg
     cp -p "all-exported-files-from-above" ~/.OS/os42.3/.gnupg/.backup/
     mv ~/.gnupg ~/.gnupg-SAVE
     mkdir ~/.gnupg; chmod 700 ~/.gnupg
6. Run the following in some vt as user "root":
     mount --bind /home/manfred/.OS/os42.3/.gnupg /home/manfred/.gnupg
7. Now log in as user "manfred" again (I use XFCE as a DE):
8. Import the secret keys:
     for key in ~/.gnupg/.backup/*-secret-*.asc; do
       gpg2 --import < "$key"
     done
9. Import the public keys:
     for key in ~/.gnupg/.backup/*-public-*.asc; do
       gpg2 --import < "$key"
     done
10. Import owner trustdb:
     gpg2 --import-ownertrust < ~/.gnupg/.backup/ownertrust-gpg.txt
11. Define my default GPG key:
     echo "default-key manfred.h@gmx.net" >> ~/.gnupg/gpg.conf
12. Test with thunderbird and enigmail-1.9.9-9.1:
     EVERYTHING's OK
13. Upgrade enigmail:
     sudo zypper in -t patch openSUSE-2018-470
14. Test again with thunderbird and enigmail-2.0.4-12.1:
     ENCRYPTED E-MAILs CANNOT BE DECRYPTED
15. Downgrade to enigmail-1.9.9-9.1:
     sudo zypper in --oldpackage enigmail-1.9.9-9.1
16. Test again with thunderbird and enigmail-1.9.9-9.1:
     WORKS AGAIN AS USUAL, i.e. ENCRYPTED E-MAILs CAN BE DECRYPTED AGAIN

Note: I never booted into any other OS during the above commands, hence I
always only used gpg2-2.0 from Leap 42.3, hence2 no conversion of the key
format should have happened.

Do you agree that this should have worked?