Merge pull request #9687 from Carreau/memory-history

Precise you can use `:memory:` for the history

IPython/core/history.py

@@ -162,6 +162,9 b' class HistoryAccessor(HistoryAccessorBase):'
         
             ipython --HistoryManager.hist_file=/tmp/ipython_hist.sqlite
         
+        you can also use the specific value `:memory:` (including the colon
+        at both end but not the back ticks), to avoid creating an history file.
+        
         """).tag(config=True)
     
     enabled = Bool(True,