+N refs animation edge case

[fbstj]

if you hover over the end of the +N extra branches label in the Commits list it can cause animation flicker where the +N is removed which "shrinks" the label from under the mouse cursor causing animation cancellation then looping when the +N is added back in.

in the case i found it was O local/master +2 and hovering close to the border would be enough to trigger the looping, as either the eventual label wasn't long enough or the in-between state was enough to cause cancellation.

[GitFiend]

Yeah, it's a bit flaky right now. I'm thinking of changing this so that you need to click on the +2 to expand the stack. I want to move away from hover effects that move elements around.