patch 8.0.1237: ":set scroll&" often gives an error commit https://github.com/vim/vim/commit/af2d20c6285c1d2973e3d9b5e8f727e3ed180493 Author: Bram Moolenaar <Bram@vim.org> Date: Sun Oct 29 15:26:57 2017 +0100 patch 8.0.1237: ":set scroll&" often gives an error Problem: ":set scroll&" often gives an error. Solution: Don't use a fixed default value, use half the window height. Add a test. (Ozaki Kiichi, closes #2104)

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