Appstore multiple update of the same application
The log of your updates are available in:

~/Library/Application Support/App Store/updatejournal.plist


The simple solution is to clear the update logs by deleting the mentioned file. 

Here is the guide to remove duplicate if you want to keep the update logs.


Open Terminal.
Convert the updatejournal.plist by entering this line plutil -convert xml1 then drag the updatejournal.plist from Finder into Terminal to expand the path, then press Return. Mine is the following:

plutil -convert xml1 ~/Library/Application\ Support/App\ Store/updatejournal.plist 

Open ~/Library/Application\ Support/App\ Store/updatejournal.plist with your favorite text editor (TextEdit works fine).
Find the duplicate update logs. For example, mine is Command Line Tools (OS X 10.10). The point is to delete that entry which is inside the scope of &lt;dict&gt;. So you should delete the content between &lt;dict&gt; and &lt;/dict&gt;. Here is line I need to delete. Save the file.

&lt;dict&gt;
    &lt;key&gt;__isSoftwareUpdate&lt;/key&gt;
    &lt;true/&gt;
    &lt;key&gt;installDate&lt;/key&gt;
    &lt;date&gt;2014-10-17T09:55:17Z&lt;/date&gt;
    &lt;key&gt;productKey&lt;/key&gt;
    &lt;string&gt;031-08844&lt;/string&gt;
    &lt;key&gt;release-notes&lt;/key&gt;
    &lt;string&gt;Command Line Developer Tools for OS X 10.10&lt;/string&gt;
    &lt;key&gt;title&lt;/key&gt;
    &lt;string&gt;Command Line Tools (OS X 10.10)&lt;/string&gt;
    &lt;key&gt;version&lt;/key&gt;
    &lt;string&gt;6.1&lt;/string&gt;
&lt;/dict&gt;

Convert the file back to binary1 by entering this line plutil -convert binary1 and drag the updatejournal.plist from Finder, and press Return. Here is mine in Terminal:

plutil -convert binary1 ~/Library/Application\ Support/App\ Store/updatejournal.plist 

Open Mac App Store and refresh the Updates section. The duplicate line should disappear. Remember to only delete one entry of duplicate file. Imagine that plist as a spreadsheet with duplicate lines. Just delete one.


Feel free to leave question in comment if the tutorial is vague.