how to keep .emacs files in synch

[kj <socyl@987jk.com.invalid>]

I regularly work on various systems, and it's a bit of a chore to
keep my .emacs files in synch.  I've tried various approaches, none
entirely satisfactory.  The two issues that give me the most
headaches are 1) to automate the process whereby changes to one
system's .emacs file gets reflected on the .emacs files on other
systems; and 2) to manage those modifications that are applicable
to only one or a subset of the systems.

I'd be interested to read how others solve this problem.

Thanks!

kj
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NOTE: In my address everything before the first period is backwards;
and the last period, and everything after it, should be discarded.