I have firefox, thunderbird, thunderbird-locale-en, thunderbird-locale-en-us, xul-ext-calendar-timezones, xul-ext-gdata-provider and xul-ext-lightning pinned in Synaptic.
When I run apt-get upgrade. I get the following
The following packages will be upgraded:
boot-repair boot-sav darktable firefox libvlc5 libvlccore5 thunderbird thunderbird-locale-en
thunderbird-locale-en-us vlc vlc-data vlc-nox vlc-plugin-notify vlc-plugin-pulse
xul-ext-calendar-timezones xul-ext-gdata-provider xul-ext-lightning
17 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 53.0 MB of archives.
After this operation, 606 kB of additional disk space will be used.
Do you want to continue [Y/n]?
Are these packages really going to be upgraded?
Yes they are going be upgraded.
You have to hold them with dpkg:
Reference: Ubuntu Help