[haskeline] #97: add flags to control whether duplicates in history should be preserved

[haskeline]

#97: add flags to control whether duplicates in history should be preserved
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Reporter:  phercek      |       Owner:     
    Type:  enhancement  |      Status:  new
Priority:  major        |   Milestone:     
 Version:               |    Keywords:     
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 Add flags historyIgnoreDuplicates and historyIgnoreAllDuplicates.

 historyIgnoreDuplicates
 Do not enter command lines into the history list if they are duplicates of
 the previous event.

 historyIgnoreAllDuplicates
 If a new command line being added to the history list duplicates an older
 one, the older command is removed from the list (even if it is not the
 previous event).

 This is just to keep the usefull stuff in history so that users do not
 need to have it too long to make sure interesting items are not evicted by
 repeated use of few commands. Even the next/previous history item
 retrieval works better with these.

-- 
Ticket URL: <http://trac.haskell.org/haskeline/ticket/97>
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