Please show 'ls -ld /usr/share/doc/libglib2.0*'. I'm pretty sure one of the directories is wrongly symlinked to the other, which means that unpacking libglib2.0-data after libglib2.0-0 *overwrites* the libglib2.0-0 changelog /on the filesystem/.
This is a classic botched symlink->directory migration in a package.
Please show 'ls -ld /usr/share/ doc/libglib2. 0*'. I'm pretty sure one of the directories is wrongly symlinked to the other, which means that unpacking libglib2.0-data after libglib2.0-0 *overwrites* the libglib2.0-0 changelog /on the filesystem/.
This is a classic botched symlink->directory migration in a package.