The rail slides away and your commits show their diff
Collapsing the navigation now slides the rail first and settles the feed after, keeping the commit under your cursor in place. Text that re-wraps flashes red and green gutter marks, like a diff you didn't ask for.
Click the collapse button in the navigation and the rail slides from 256 pixels wide to 80 in 300 milliseconds while the feed holds still. The commit in the middle of your screen keeps its place. Only when the slide ends does text that needs more lines fade, re-wrap once and fade back, with red minus marks down its left edge, green plus marks down its right, and a small @@ -4 +3 @@ chip beside the hash.
Credit goes to xHeaven, who wrote the choreography. The slide runs 300 milliseconds, the grow 200, the fade out 120 and the fade in 180, and the marks clear after 1.3 seconds. Only commits within a screen of your viewport take part. The rest skip layout entirely. Images keep their height during the slide, then grids ease from 288 to 384 pixels tall and single pictures up to 684, so the column has somewhere to grow.
One catch. The gutter marks assume every line is the same height. Drop a code block into a commit that re-wraps and the minus and plus signs drift out of line with the words beside them.