+
+local function foldlevel(lnum, exclude_start)
+ if lnum < 1 or lnum > vim.api.nvim_buf_line_count(0) then
+ return 0
+ end
+ local value = vim.treesitter.foldexpr(lnum)
+ local level = tonumber(value:match('%d+')) or 0
+ -- A '>N' starts a new fold even when adjacent folds have the same level.
+ return math.max(0, level - (exclude_start and value:sub(1, 1) == '>' and 1 or 0))
+end
+
+function _G.DotfilesFoldExpr()
+ local line = vim.v.lnum
+ -- Keep only levels spanning the previous, current, and next lines.
+ -- Default foldminlines keeps interiors of fewer than two lines visible.
+ return math.min(foldlevel(line - 1), foldlevel(line, true), foldlevel(line + 1, true))
+end
+
+local function enable(buf)
+ vim.wo[0][0].foldexpr = '0'
+ if not pcall(vim.treesitter.start, buf) then
+ return
+ end
+
+ vim.wo[0][0].foldexpr = 'v:lua.DotfilesFoldExpr()'
+ vim.wo[0][0].foldmethod = 'expr'
+end
+
+vim.api.nvim_create_autocmd('FileType', {
+ callback = function(args) enable(args.buf) end,
+})
+
+-- Startup filetype detection can precede this config being sourced.
+if vim.bo.filetype ~= '' then
+ enable(0)
+end