On 2021-03-25 04:39 -0400, Michael Grant wrote:
When I apt-update, sometimes I update something for which I modified a config file and I get this menu:
Configuration file '/etc/matrix-synapse/homeserver.yaml'
==> Modified (by you or by a script) since installation.
==> Package distributor has shipped an updated version.
What would you like to do about it ? Your options are:
Y or I : install the package maintainer's version
N or O : keep your currently-installed version
D : show the differences between the versions
Z : start a shell to examine the situation
The default action is to keep your current version.
*** homeserver.yaml (Y/I/N/O/D/Z) [default=N]
This prompt is coming from dpkg which notes that a conffile has been
changed. In Debian/dpkg jargon, a conffile is a configuration file that
is shipped in a package. The dpkg program keeps a checksum for each
conffile in its database and can therefore detect modifications, but it
does not track the content of conffiles.
Sometimes, rarely, I get a 5th option offering to try to merge the
files. I don't know what causes the merge option to be available or
not.
These packages use a different mechanism for their configuration files
based on a program called ucf. The files are _not_ shipped in the
package, but created from a template in the maintainer scripts. Unlike
dpkg, ucf also stores the content of these files and is therefore able
to offer merge options.
Is there some way I can at minimum add a 5th option to the above menu
to run emacs in emerge mode with those files as args? This would save
lazy me the steps of echoing the vars and starting emacs manually.
I run etckeeper, it would be really sweet if this was smart enough to
attempt a 3-way merge (merge with an ancestor file).
I am afraid this is not easily possible. Making dpkg's conffile prompt
smarter has been requested many times, but nothing has happened since
bug #32877[1] and its many siblings have been filed. Yes, that bug is
22 years old.
Cheers,
Sven
1. https://bugs.debian.org/32877