I created a simple ifcfg-eth0, like so:

DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes

and brought it up, ensured it worked. Then I ran virt-manager, created a bridge, and told it to bridge the eth0 interface and copy the configuration to the bridge. The resulting ifcfg-br1 looks like this:

DEVICE=br1
ONBOOT=no
TYPE=Bridge
BOOTPROTO=none
IPADDR=192.168.122.211
NETMASK=255.255.255.0
IPV6INIT=yes
IPV6_AUTOCONF=no
DHCPV6=no
IPV6ADDR=fe80::5054:ff:fec8:6cb5/64
STP=on
DELAY=0.0

ONBOOT=no is OK as that was an option during bridge creation, but the important thing is that it hasn't configured "BOOTPROTO=dhcp" as it should. Instead it's taken the IP addresses that were *currently* assigned to the interface via DHCP, and set up static addressing using those addresses. I'm pretty sure that's not what people would expect when 'copying' the configuration in this way.

Tested on virt-manager 1.0.1-3.fc21.1.noarch .