Current behaviour:
speedbar-expand-line-descendants incorrectly recursively expands all nodes
below the current node.

Expected behaviour:
Should only recursively expand descendants of the current node.

Steps to reproduce:
emacs -Q ~
M-x speedbar
<focus to speedbar>
<cursor over a directory that is not the last in list>
[

("[" is bound to `speedbar-expand-line-descendants')

Found in: GNU Emacs 26.1

-- 
Kieran Barry -- kieranb@google.com
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