CTAN has a new package: texdiff

[CTAN Announcements]

This will reach your local mirror within a day.

Jim Hefferon
Saint Michael's College

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The following information was provided by our fellow contributor:

Name of contribution: texdiff
Version number: 0.4
Author's name: Cengiz Gunay
Location on CTAN: /support/texdiff
Summary description: Compares two (La)TeX documents to create a merged version showing 
  changes, similar to that of 'Change Tracking' in some word processors.
License type: artistic

Announcement text: 
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The first two files are compared and a new TeX 
file is output. When the output file is processed 
with (La)TeX it marks new changes with blue and 
old text with red with a strike-through line. 
Furthermore, passages with changes are marked at 
the margin with grey bars by the LaTeX changebar 
package.
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This package is located at 
   http://tug.ctan.org/tex-archive/support/texdiff
.  More information is at
   http://tug.ctan.org/pkg/texdiff
(if the package is new it may take a day for that information to 
appear).  We are supported by the TeX Users Group http://www.tug.org .  
Please join a users group; see http://www.tug.org/usergroups.html .