refactor(git): scratch buffers wipe by default, consolidate factories in util

lua/git/diff.lua

@@ -3,35 +3,6 @@ local util = require("git.util")
 
 local M = {}
 
----@class ow.Git.EmptyBufOpts
----@field name string?
----@field bufhidden ("hide"|"wipe")?  defaults to "wipe"
-
----Build a read-only scratch buffer, optionally naming it. When `opts.name`
----is set and a loaded buffer with that name already exists, returns it
----instead of creating a duplicate.
----@param opts ow.Git.EmptyBufOpts?
----@return integer
-function M.empty_buf(opts)
-    opts = opts or {}
-    if opts.name then
-        local existing = vim.fn.bufnr(opts.name)
-        if existing ~= -1 and vim.api.nvim_buf_is_loaded(existing) then
-            return existing
-        end
-    end
-    local buf = vim.api.nvim_create_buf(false, true)
-    vim.bo[buf].buftype = "nofile"
-    vim.bo[buf].bufhidden = opts.bufhidden or "wipe"
-    vim.bo[buf].swapfile = false
-    vim.bo[buf].modifiable = false
-    vim.bo[buf].modified = false
-    if opts.name then
-        pcall(vim.api.nvim_buf_set_name, buf, opts.name)
-    end
-    return buf
-end
-
 ---Name a buffer and re-run filetype detection from the (re-)set name.
 ---Wrapped in `pcall` because a buffer with that name may already exist
 ---(E95).