How to selectively enable/disable old_or_new.repo files effectively

[Barry Yu]

I downloaded all fc3 rpm update packages and put them into a folder
/mnt/update/fc3update/, and used createrepo to issue ;

createrepo /mnt/update/fc3update/

The process started and finally finished and displayed;

saving primary metadata
saving file lists metadata
saving other metadata

( 2 folders "headers" and "repodata" are created under 
/mnt/update/fc3update/ )

    *    *
Next I created a /mnt/yum.repos.d/fc3update.repo and the contents are ;

[fc3update]
name=FC3 rpm updates
baseurl=file:///mnt/update/fc3update/
enabled=0    

    *    *
In /etc/yum.conf I disabled gpgcheck from 1 to 0,

    *    *
I started to update my fc3 with commands;

yum --disablerepo=fedora.repo --disablerepo=fedora-updates.repo 
--enablerepo=fc3update.repo -y

(By default the fedora.repo and fedora-update.repo both are enabled=1 
and I intended to disable
them, I just wanted to use fc3update.repo)

After a while I got message "Error getting repository data for for 
fedora.repo, repository not
found"

Obvious the above process failed, my questions:

When I add a new repo file into /etc/yum.repos.d/, and want to 
selectively enable/disable a
specific xxxx.repo file, is the following a correct syntax "yum 
--disablerepo=file1.repo --disablerepo=file2.repo
--enablerepo=file3.repo"  ? (if yes, why I failed above ?)
What have I missed ?

*********
An alternative way enables me to accomplish my goal,with same files and 
folders used in above and I
made some minor changes ;

fedora.repo - change the enabled=1 from 1 to 0
fedora-update.repo - change the enabled=1 from 1 to 0
/etc/yum.conf - gpgcheck changed from 1 to 0.
(Any command to replace the manual change ?)

And then I issued command : yum update

(The update starts)
Update: xxxxx.i386 0:6.1.-12.fc321
Update: xxxxxxxx

Other transactions:
Obsoleting: xxxxxxxxxxxx.fc3
Obsoleting: xxxxxxxxxxxxxxx.fc3

Is  this ok [Y/N]: y
Downloading Packages:

Running Transaction Test
Fished Transaction Test
Transaction Test Succeeded
Running Transaction
Updating : bash 100% done 1/400
updating : xxxxx 100% done 2/400

completing update for xxxx - 1/400


cinoketubg update for xxxxxx - 400/400

Installed: kernel.i686 0:2.6.9-1.681_FC3
Updated: abiword.i386xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxx
Obsoleted: boost.i386 xxxxxxxxxxxxx
Completed!