Split history configuration to its own file
Confirm history expansions

I would like to become proficient at using more complex history expansions in my
day-to-day machine interactions, but do not yet trust myself to get these right
first go.  Training wheels, if you will.
Disable swapfile when in diff mode

I will likely have these files open in my 'edit' vim session when diffing them.
Since I store my swapfiles in the same place, opening the origin files in diff
mode will trigger 'swapfile already exists' complaints.
Use latest DrChip's sh syntax file
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