Tags: patch

This patch just adds some tests so I don't think that should be too
controversial

I have included some comments in the patch that I would like to talk
about though.

In the test `em-hist-test/eshell-history-file-name/nil' we don't save
any history to a file because `eshell-history-file-name' is nil and the
environment variable HISTFILE is unset.  I would like to see some user
visible warning here.  In theory this could be intended behavior to
prevent any history from being saved to disk but I think the more likely
case is the user accidentally misconfigured it.


I added a comment to the existing test
`em-hist-test/write-history/overwrite-multiple-shells' as I don't like
the behavior it demonstrates.  I was experiencing the occasional history
loss for years before I finally decided to investigate and now I know to
set `eshell-history-append' to true.

While writing this email I discovered Bug#66700 which seemed to come to
the conclusion that we should set `eshell-history-append' to true in the
next version of Emacs.  However, this would effectively make
`eshell-hist-ignoredups' useless.  I would be interested in a solution
where we check if the histfile has been updated to make sure we
overwrite without history loss.