The situation is that you perform a rebase, and one of the commits becomes empty
during the rebase, in a way that couldn't be predicted before the rebase
started. To explain: git rebase has some logic where it immediately discards
commits if it can tell that they already exist in the branch being rebased onto;
it does this by looking at the patch ids of the commits to work out which
commits already exist upstream. But for those commits that become empty even
though there isn't a corresponding commit upstream, git stops with an error, and
lazygit detects this (in CheckMergeOrRebaseWithRefreshOptions) and automatically
continues the rebase.
This all works fine; I'm adding this test because I almost broke this during
development of this branch, so I'm adding it to guard against regressions.
e1eb95b2b3