In order to view the modified file log over the web interface, you must use the gitweb_sonic template. First create a folder called sonichgv2m102 in the htdocs folder (assuming you have apache running). Copy over the files in the sonichgv2m102/static folder to this newly created directory. Then modify the HGRC file of the repo to include:
[extensions] sonic=/path/to/sonichgv2m102/hgext/sonic.py sonicweb=/path/to/sonichgv2m102/hgext/sonicweb.py
[web] templates=/path/to/sonichgv2m102/templates style=gitweb_sonic staticurl=http://yourserver.com/sonichgv2m102 encoding=UTF-8
Now if you go to the repo web UI and click on the files link on the top you can browse the directory contents (manifest). Click on a "revisions" link of a file and you will see the modified file log page:
The file revision is on the left most column. Note that file revisions start from 0. The next number is the commit revision in which the file was modified. The author of that commit is shown in the file log page as well. You will see a link for "fulldiff" on the right, that will show side-by-side diffs of the file.
You can also use the radio buttons to select 2 versions of the file and diff them side-by-side.