feat(git): open commits from gitlog in the same window

lua/git/show.lua

@@ -127,9 +127,14 @@ local function show_diff(ctx, section)
     vim.api.nvim_set_current_win(left_win)
 end
 
+---@class ow.Git.OpenCommitOpts
+---@field split (false|"above"|"below"|"left"|"right")?  forwarded to `git.new_scratch`. Default opens a new horizontal split.
+
 ---@param worktree string
 ---@param ref string
-function M.open_commit(worktree, ref)
+---@param opts ow.Git.OpenCommitOpts?
+function M.open_commit(worktree, ref, opts)
+    local split = opts and opts.split
     repo.rev_parse(worktree, ref, true, function(resolved)
         local sha = resolved or ref
         local name = "git://" .. sha .. "//"
@@ -137,13 +142,18 @@ function M.open_commit(worktree, ref)
         -- are immutable so the content is stable.
         local existing = vim.fn.bufnr(name)
         if existing ~= -1 and vim.api.nvim_buf_is_loaded(existing) then
-            vim.api.nvim_open_win(existing, true, {
-                split = vim.o.splitbelow and "below" or "above",
-            })
+            if split == false then
+                vim.cmd.normal({ "m'", bang = true })
+                vim.api.nvim_set_current_buf(existing)
+            else
+                vim.api.nvim_open_win(existing, true, {
+                    split = split or (vim.o.splitbelow and "below" or "above"),
+                })
+            end
             return
         end
 
-        local buf, win = git.new_scratch({ name = name })
+        local buf, win = git.new_scratch({ name = name, split = split })
         vim.b[buf].git_worktree = worktree
         vim.b[buf].git_ref = sha
 
@@ -157,10 +167,11 @@ function M.open_commit(worktree, ref)
                         ref,
                         vim.trim(result.stderr or "")
                     )
-                    -- Tear down the empty placeholder window+buffer so a
-                    -- retry runs a fresh fetch instead of hitting the
-                    -- cached-buffer branch and reopening an empty pane.
-                    if vim.api.nvim_win_is_valid(win) then
+                    -- Drop the empty placeholder so a retry runs a fresh
+                    -- fetch. With `split = false` the window falls back to
+                    -- its alternate buffer (the gitlog); for a real split
+                    -- we close the dedicated window to keep the layout tidy.
+                    if split ~= false and vim.api.nvim_win_is_valid(win) then
                         pcall(vim.api.nvim_win_close, win, true)
                     end
                     if vim.api.nvim_buf_is_valid(buf) then