In 0d195077e4 we improved the performance of the status bar spinner by
avoiding a layout. This is fine from one spinner tick to the next, but it's a
problem when spinning starts or ends (or in the hypothetical case that the
status text changes in the middle of the operation, which we never do in
lazygit, but theoretically could). In this case a layout is needed so that the
rest of the status bar gets pushed over appropriately (or moves back to the left
when the spinner ends), and also so that the bottom line is shown or hidden
properly for users who set gui.showBottomLine to false.
To fix this, keep track of the status string width and force a layout whenever
it changes. This includes the beginning and end of an operation when it changes
from empty to non-empty or vice versa.
There is currently no observable misbehavior from this bug, but that's only
because we must have a HandleRender call somewhere that forces a full layout
when an operation starts or ends. We will remove the Render() call from
HandleRender at the end of this branch, at which point the misbehavior would be
visible if we didn't fix it here.
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