Instead of a user config that always shows a selection on focus, the
focused main view starts without a selection (matching master). Pressing
<space> shows a selection in the middle of the view (no scrolling);
pressing <esc> hides it again before falling through to exiting the view.
I copied all files except dot files (.github and .gitignore), the _examples
folder, and go.mod/go.sum.
At some point we may want to copy the files back to the gocui repo when other
clients (e.g. lazydocker) want to use the newer versions of them.
When switching to a different repo, and then back to the original one, searching
would no longer work. The reason is that our contexts set callbacks on their
views; when switching to a different repo we instantiate a new set of contexts,
so they will overwrite the views' callbacks with their new ones, but when
switching back to the original repo, we reuse the old contexts because they are
still in memory, but they won't set their callbacks again since they only do
this on construction.
To fix this, replace the view-local callbacks with a global one on the gui that
takes the view as an argument, so that the callback can look up the associated
context dynamically.
In this commit this is only possible by pressing '0' in a side panel; we'll add
mouse clicking later in the branch.
Also, you can't really do anything in the focused view except press escape to
leave it again. We'll add some more functionality in a following commit.
