I'm not a skilled UI designer, so I suspect there may be even better
options, but it's definitely already better than the raw ASCII "---" we
had before.
Put the line only at the beginning because it looks bad if the line
after the label is misaligned when labels don't have the same width
(e.g. "Remote" vs. "Local" in the divergence view).
A common issue I have is that I want to move a commit from the top of my branch
all the way down to the first commit on the branch. To do that, I need to navigate
down to the first commit on my branch, press 'e' to start an interactive rebase,
then navigate back up to the top of the branch, then move my commit back down to
the base. This is annoying.
Similarly annoying is moving the commit one-by-one without explicitly starting
an interactive rebase, because then each individual step is its own rebase which
takes a while in aggregate.
This PR allows you to press 'i' from the commits view to start an interactive
rebase from an 'appropriate' base. By appropriate, we mean that we want to start
from the HEAD and stop when we reach the first merge commit or commit on the main
branch. This may end up including more commits than you need, but it doesn't make
a difference.
