* `HISTORY_SUBSTRING_SEARCH_PREFIX` is a global variable that defines
how the command history will be searched for your query. If set to a non-empty
value, only history prefixed by your query will be matched. For example,
if this variable is empty, `ls` will match `ls -l` and `echo ls`; if it is
non-empty, `ls` will only match `ls -l`.
Co-authored-by: Xue Qianming <qianmingxue@microsoft.com>
