I am trying to make etckeeper track /etc and another folder in /.

However the script 20-warn-problem-files reports many errors like

find: `./proc/7010/task/7010/fd/5': No such file or directory
find: `./proc/7010/task/7010/fd/5': No such file or directory
find: `./proc/7010/task/7010/fd/5': No such file or directory
find: `./proc/7010/task/7010/fdinfo/5': No such file or directory
find: `./proc/7010/task/7010/fdinfo/5': No such file or directory
find: `./proc/7010/task/7010/fdinfo/5': No such file or directory

Due to files in /proc being created and deleted while find is running.

I am not sure why find needs to run at all, when instead one could analyze the output of git ls-files and see if any of those files are problematic.

Using etckeeper to track all of / is not a supported use case. You're free to try to use etckeeper that way, but when it breaks, you get to modify it to work yourself, and it seems unlikely that the resulting patches would be suitable to be applied to etckeeper.

So wontfix, sorry. --?Joey