When editing a commit, the index of the current commit can change; for example,
when merge commits are involved, or when working with stacked branches where
"update-ref" commands may be added above the selected commit.
Reselect the current commit after pressing "e"; this requires doing the refresh
blocking on the main thread. (Another option that I considered was to use a
SYNC refresh, and then select the new line with an OnUIThread inside the Then
function. This also works, but results in a very visible lag.)
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