question about building mesa with the two scripts from Xorg wikis

[Joe Smith]

Hi,

I noticed a discrepancy in the Xorg documentation that's been causing me some confusion:

At http://wiki.x.org/wiki/ModularDevelopersGuide:
When using the build.sh script, it says:
"If you want to include Mesa/OpenGL support in the X server, you will need unpack the Mesa source code and pass the directory of the Mesa sources to the build.sh script."  
And you pass the mesa directory like this:
-m path-to-mesa-sources-for-xserver : full path to Mesa sources

Also, in the build.sh script, building the mesa sources is commented out, like this:  #build mesa mesa.

While at http://www.x.org/wiki/Development/git:
The mesa sources are built before the xserver, and the sources directory is *not* passed to the xserver build directives.

So the questions are: 
1) Does mesa need to be built separately, as demonstrated in the second link?  If so, why is it commented out in build.sh?
2) Should the --with-mesa-source parameter always be used, and if so, why is it not used in the second link?

Thanks for your time.