refactor(git): share builder between git_show_buf and git_show_blob

lua/git/diff.lua

@@ -74,20 +74,23 @@ local function read_show(worktree, revspec)
     return util.split_lines(result.stdout or "")
 end
 
+---Internal builder: run `git show <revspec>`, drop the result into a fresh
+---scratch buffer, and (when `is_index` is true) wire up the BufWriteCmd
+---that writes back to the git index for `index_path`.
 ---@param worktree string
----@param ref string '' for index, 'HEAD' or a sha for committed refs
----@param path string
----@param is_index boolean? true to hook :w to update the git index
+---@param revspec string
+---@param is_index boolean
+---@param index_path string?  required when is_index is true
 ---@return integer
-function M.git_show_buf(worktree, ref, path, is_index)
-    local lines = read_show(worktree, ref .. ":" .. path)
+local function build_show_buf(worktree, revspec, is_index, index_path)
+    local lines = read_show(worktree, revspec)
     local buf = vim.api.nvim_create_buf(false, true)
     vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
     vim.bo[buf].buftype = is_index and "acwrite" or "nofile"
     vim.bo[buf].bufhidden = "wipe"
     vim.bo[buf].swapfile = false
     if is_index then
-        attach_index_writer(buf, worktree, path)
+        attach_index_writer(buf, worktree, assert(index_path))
     else
         vim.bo[buf].modifiable = false
     end
@@ -95,19 +98,20 @@ function M.git_show_buf(worktree, ref, path, is_index)
     return buf
 end
 
+---@param worktree string
+---@param ref string '' for index, 'HEAD' or a sha for committed refs
+---@param path string
+---@param is_index boolean? true to hook :w to update the git index
+---@return integer
+function M.git_show_buf(worktree, ref, path, is_index)
+    return build_show_buf(worktree, ref .. ":" .. path, is_index or false, path)
+end
+
 ---@param worktree string
 ---@param blob string  the blob SHA (full or abbreviated)
 ---@return integer
 function M.git_show_blob(worktree, blob)
-    local lines = read_show(worktree, blob)
-    local buf = vim.api.nvim_create_buf(false, true)
-    vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
-    vim.bo[buf].buftype = "nofile"
-    vim.bo[buf].bufhidden = "wipe"
-    vim.bo[buf].swapfile = false
-    vim.bo[buf].modifiable = false
-    vim.bo[buf].modified = false
-    return buf
+    return build_show_buf(worktree, blob, false, nil)
 end
 
 ---@class ow.Git.EmptyBufOpts