From the Mailing list:

• qt/main.cpp: Pass pinentry info to PinEntryDialog constructor. Set save passphrase checkbox text from pinentry_t->default_pwmngr.
• qt/pinentrydialog.cpp, qt/pinentrydialog.h: Dialog now accepts pinentry info in the constructor and removed unneeded setter for pinentry info. Add save passphrase checkbox.

This patch adds functionality to save key passphrases with pinentry-qt
that already exists in pinentry-gtk-2.

A "save passphrase" checkbox is shown when libsecret is available,
the external password cache is enabled, and there is valid data in
pinentry_t->keyinfo. When checked, the pinentry info is updated to allow
the underlying implementation in pinentry/pinentry.c and
pinentry/password-cache.c to cache the password using libsecret.