When you perform a TeX Live update, the specific packages that were updated is logged in tlmgr.log
(located in ~/texmf-var/web2c/
). It looks like this:
...
[Thu Jan 30 16:39:24 2014] update: sa-tikz (32788 -> 32815)
[Thu Jan 30 16:39:28 2014] update: texlive-msg-translations (32801 -> 32813)
[Thu Jan 30 16:39:32 2014] update: texlive-scripts (32798 -> 32811)
[Thu Jan 30 16:39:35 2014] update: xetex-itrans (24105 -> 32810)
[Fri Jan 31 13:56:10 2014] update: babel-spanish (30295 -> 32825)
[Fri Jan 31 13:56:25 2014] update: pst-3dplot (27233 -> 32824)
You see the date of the update/install, as well as the type (whether it was a removal/install/update/...), the name of the package, as well as the update revision reference (from -> to).
Now you can visit TeX Live Master trunk and enter the revision number as see the changes. For example, the above revision to 32824 lists:

tlmgr
window.tlmgr
I could find on that link? Nice!