Hi all,

This is my first time doing this so sorry if there are some mistakes in the
process. I am also not entirely accustomed to elisp so please forgive my
code and provide any feedback you may have.

These new changes allow the user to select a container when connecting to a
kubernetes pod. This is essential for kubernetes Tramp functionality since
the first container may not always be the desired pod. Many pods contain
multiple side-car containers besides the main application container.

Now considering the above, the below changes are not the most desirable
from my perspective. From a user perspective, there are no visual cues to
display what container you selected. I wanted to avoid using ":" separator
between a pod and container since that might overload the meaning of that
separator.

The other issue is the change to tramp-expand-args which now can expect
either a lambda or string. The lambda takes in the entire tramp-file-name
struct but that can be reduced to just passing the pod name for the sake of
kubernetes connections. At the very least this should warrant a function
rename, but I could also see a possible break off to more specific handling
for kubernetes. Currently, Emacs is only accounting for connecting to pods,
but jobs are still relevant when it comes to kubernetes which would require
some selection.

Changes can also be found at
https://github.com/Aaronzinhoo/emacs/tree/feat-tramp-kubernetes-select-container
if needed.