Only append entry to REPL history if it is not the same as last entry

[Alexander-Block]

Closes #75.
A REPL entry is only appended to the REPL history if it is not a duplicate of the last entry.

[byorgey]

Thanks! This all looks good, however it looks a bit strange because we also use the REPL history for deciding what to display in the REPL. So if you enter the same as the previous entry, the output shows up again but your input is not shown:

Ideally the input should still be shown a second time in the REPL window, but when you use the up/down arrow keys it will only show up once.

I guess one way to solve this would be to add another Boolean field to a REPLEntry saying whether it is a duplicate, and then to ignore such entries when scrolling through the history with up/down.

[Alexander-Block]

Thank you for pointing out this strange behaviour; somehow I overlooked this.
I agree that it is necessary then not to completely discard duplicate REPL entries. I have implemented your proposal to mark duplicate entries using a second Boolean field in a REPLEntry and filter duplicates out only when scrolling through the history with up/down.

[byorgey]

Works great, thanks!