Didn't want to answer my own question but I think it may be helpful for future reference for people with the same problem.
Well, I managed to perform a search within the 'log messages' (cvs term for the commit commentaries) filtering by the content of the text in the log message and group the files changed on that commit.
As pointed out by 'Joakim Elofsson' here, cvsps is a good tool for grouping commit information in 'patch sets' which are individual commits with references to all the files changed in those commits.
I used the version of cvsps packed for cygwin as at this moment there's no port for windows.
Just install the cygwin with the internet setup available here and, when choosing packages, search for cvsps and cvs, install both.
I couldn't manage to use the checked out files on my system (through the /cygdrive/c folder) so I checked them out from the cygwin shell.
BEGIN Obs for tortoise users
You'll need to setup CVSROOT environment var to the current CVSROOT of your repository by the command:
export CVSROOT="Your CVSROOT string here"
Usually, if check the properties page of any file of your checked out code base there will be a tab named CVS. There'll be your CVSROOT string. (if you're using :sspi: to connect to your remote repository as I do, you may try to switch it to :pserver:, it did work for me but I don't know exactly why).
END Obs for tortoise users
Well, after checking out your repository use command:
cvsps
This will create the cvsps patchset base for your requests. Then use:
cvsps -l "Some regexp code"
It will search the patch sets for log messages matching the input regexp.
This is a sample from using cvsps -l
P100-PR-FEX` on my database (changed some filenames and paths for being able to make it public...):
PatchSet 71
Date: 2012/10/25 11:30:44
Author: GUARITA
Branch: HEAD
Tag: (none)
Branches:
Log:
Kind: Error correction
Trace: P100-PR-FEX145
Description:
Corrections of the TRUE and FALSE conventions used by the C++ (true:everything but 0, false:0) P100 interface to the VB6 (false:0, true:-1 or 'all bits set to 1 which is -1 in 2's complement') P100Interface ActiveX object.
P100 Panel Version increment.
Members:
SidePanels/P100.wimp:1.2->1.3
SidePanels/Calcs/P100Interface/private/P100Interface.cpp:1.2->1.3
You may also use it to compare changes between tags (which I use to control releases) with cvsps -r <tag1> -r <tag2>
.