chore: rename and simplify help update script

scripts/update-help.sh

@@ -0,0 +1,33 @@
+#!/bin/sh
+
+# run after changing nvim-tree.lua DEFAULT_OPTS or nvim-tree/actions/init.lua M.mappings
+# scrapes and updates nvim-tree-lua.txt
+# run from repositry root: scripts/update-default-opts.sh
+
+
+begin="BEGIN_DEFAULT_OPTS"
+end="END_DEFAULT_OPTS"
+
+# scrape DEFAULT_OPTS, indented at 2
+sed -n -e "/${begin}/,/${end}/{ /${begin}/d; /${end}/d; p; }" lua/nvim-tree.lua > /tmp/DEFAULT_OPTS.2.lua
+
+# indent some more
+sed -e "s/^  /      /" /tmp/DEFAULT_OPTS.2.lua > /tmp/DEFAULT_OPTS.6.lua
+
+# help, indented at 6
+sed -i -e "/${begin}/,/${end}/{ /${begin}/{p; r /tmp/DEFAULT_OPTS.6.lua
+           }; /${end}/p; d; }" doc/nvim-tree-lua.txt
+
+
+begin="BEGIN_DEFAULT_MAPPINGS"
+end="END_DEFAULT_MAPPINGS"
+
+# generate various DEFAULT_MAPPINGS
+sed -n -e "/${begin}/,/${end}/{ /${begin}/d; /${end}/d; p; }" lua/nvim-tree/actions/init.lua > /tmp/DEFAULT_MAPPINGS.M.lua
+cat /tmp/DEFAULT_MAPPINGS.M.lua scripts/generate_default_mappings.lua | lua
+
+# help
+sed -i -e "/${begin}/,/${end}/{ /${begin}/{p; r /tmp/DEFAULT_MAPPINGS.lua
+           }; /${end}/p; d }" doc/nvim-tree-lua.txt
+sed -i -e "/^DEFAULT MAPPINGS/,/^>$/{ /^DEFAULT MAPPINGS/{p; r /tmp/DEFAULT_MAPPINGS.help
+           }; /^>$/p; d }" doc/nvim-tree-lua.txt