"add cdrom" should warn about possible dependency conflicts

[webchimp]

Binary package hint: synaptic

System info:
1. using gnewsense, which is free ubuntu.
2. regularly use internet update and install from synaptic - works like a charm.
3. got hold of a few debian cds which are about 4-5 months old, added cdroms and installed these:
-------------------- Latest
Commit Log for Sat Oct 27 14:13:14 2007
Upgraded the following packages:
libc6-i686 (2.3.6-0ubuntu20) to 2.3.6.ds1-13
Installed the following packages:
tightvncserver (1.2.9-21)
tzdata (2007b-1)
-------------------- Earlier
Commit Log for Sat Oct 27 14:07:37 2007
Upgraded the following packages:
libc6 (2.3.6-0ubuntu20) to 2.3.6.ds1-13
libc6-dev (2.3.6-0ubuntu20) to 2.3.6.ds1-13
libc6-i686 (2.3.6-0ubuntu20) to 2.3.6.ds1-13
Installed the following packages:
tightvnc-java (1.2.7-4)
tightvncserver (1.2.9-21)
tzdata (2007b-1)
-----------------------
Now libc6, libc6-i686, libc6-dev are broken and nothing new can be installed from either synaptic or sudo apt-get install.
-----------------------
"Edit -> Fix Broken Packages" gives this:
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.
E: Unable to correct dependencies
-----------------------
In the case of many users, this entire problem can be avoided if a warning message pops up saying something like this:
"Adding CDROM repositories that are older than you current files is risky.
Rollbacks are not possible. So, if you want to use CDROM repos,
please verify the versions of each of the programs you wish to install."

** Or implement an Undo-Install package. which could be pretty complex.
** Or maybe prompt the user to backup the entir system or the needed program and config files.
** Or maybe do it automatically and just tell the user that so-and-so is the path where he can revert to if the installs fail, as a rollback savepoint.

[webchimp (2stepsback)]

The marked widgets are probably the best place to trigger the display of the message.

[Sebastian Heinlein (glatzor)]

Mixing cd's of different distributions is always a bad idea. The question is when to tigger the alert. everytime a non-ubuntu cd was inserted?

[webchimp (2stepsback)]

So, AFAI can see, there are three situations:

1. CD is debian but non-ubuntu
2. CD is ubuntu, but earlier version
3. CD is ubuntu but later version

Case 1 typically occurs when people are told that ubuntu is based on debian and they assume things lke compatibility.
Case 2 very likely for a hasty userf who wants to fix something broken due to any reason at all, and has no access to the internet or latest copy and wants to "at least restore back to old state". If things don't go well, he breaks synaptic, like I did and it won't allow any further action!!
Case 3 should probably not be a problem, but packages can get deprecated, as well.

**************
So IMO, a broad warning at the time of pressing the "Add CDROM" button is a must.
Immaterial of which CD is about to be used.
**************
Any later second and further warnings would depend on the script that identifies the cdrom package version (if it does).