refactor(git): older-on-left placement, drop empty placeholders

lua/git/diff.lua

@@ -3,19 +3,6 @@ local util = require("git.util")
 
 local M = {}
 
----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).
----@param buf integer
----@param name string
-local function set_buf_name_and_filetype(buf, name)
-    pcall(vim.api.nvim_buf_set_name, buf, name)
-    local ft = vim.filetype.match({ buf = buf })
-    if ft then
-        vim.bo[buf].filetype = ft
-    end
-end
-
 ---Toggle a window into or out of Vim's diff mode. Goes through the
 ---`:diffthis` / `:diffoff` commands rather than `vim.wo[win].diff = X`.
 ---The command path runs Vim's full `diff_win_options` setup, which sets
@@ -25,7 +12,7 @@ end
 ---tabpage's diff group and corrupting its render.
 ---@param win integer
 ---@param enabled boolean
-local function set_diff(win, enabled)
+function M.set_diff(win, enabled)
     vim.api.nvim_win_call(win, function()
         vim.cmd(enabled and "diffthis" or "diffoff")
     end)
@@ -46,10 +33,9 @@ function M.open(left, right, vertical)
     vim.api.nvim_set_current_buf(right)
     vim.cmd.diffsplit({
         args = { left_name },
-        mods = { split = "aboveleft", vertical = vertical },
+        mods = { split = "aboveleft", vertical = vertical, keepjumps = true },
         magic = { file = false },
     })
-    vim.cmd("clearjumps")
 end
 
 ---Repoint two existing diff windows at a new pair of buffers.
@@ -63,17 +49,19 @@ end
 ---@param right_win integer
 ---@param pair ow.Git.DiffPair
 function M.update_pair(left_win, right_win, pair)
-    set_diff(left_win, false)
-    set_diff(right_win, false)
+    M.set_diff(left_win, false)
+    M.set_diff(right_win, false)
     vim.api.nvim_win_set_buf(left_win, pair.left.buf)
     vim.api.nvim_win_set_buf(right_win, pair.right.buf)
     for _, side in ipairs({ pair.left, pair.right }) do
         if side.name then
-            set_buf_name_and_filetype(side.buf, side.name)
+            util.set_buf_name(side.buf, side.name)
         end
     end
-    set_diff(left_win, true)
-    set_diff(right_win, true)
+    M.set_diff(left_win, true)
+    M.set_diff(right_win, true)
+    vim.api.nvim_win_set_cursor(left_win, { 1, 0 })
+    vim.api.nvim_win_set_cursor(right_win, { 1, 0 })
     vim.cmd.syncbind()
 end
 
@@ -92,7 +80,7 @@ local function place_pair(buf_a, buf_b, a_left, vertical)
 end
 
 ---Dispatch for `M.split` when the current buffer is a `git://<revspec>`
----URI. Placement is writable-on-the-left via `place_pair`.
+---URI. Placement follows the older-on-left convention.
 ---
 ---gd/gh: pair cur with the worktree file at the URI's path.
 ---
@@ -121,7 +109,6 @@ local function uri_split(opts, cur_buf, cur_revspec)
     end
     -- Lazy-required to break the load-time cycle with `git.object`.
     local object = require("git.object")
-    local cur_writable = cur.stage == 0
 
     if opts.revspec ~= "" and opts.revspec:find(":", 1, true) then
         local content = util.exec(
@@ -135,16 +122,21 @@ local function uri_split(opts, cur_buf, cur_revspec)
         place_pair(
             cur_buf,
             object.buf_for(worktree, opts.revspec, content),
-            cur_writable,
+            false,
             opts.vertical
         )
         return
     end
 
     if opts.revspec == "" then
-        local worktree_buf = vim.fn.bufadd(vim.fs.joinpath(worktree, cur.path))
+        local worktree_path = vim.fs.joinpath(worktree, cur.path)
+        if not vim.uv.fs_stat(worktree_path) then
+            util.warning("worktree file does not exist: %s", cur.path)
+            return
+        end
+        local worktree_buf = vim.fn.bufadd(worktree_path)
         vim.fn.bufload(worktree_buf)
-        place_pair(cur_buf, worktree_buf, cur_writable, opts.vertical)
+        place_pair(cur_buf, worktree_buf, true, opts.vertical)
         return
     end
 
@@ -153,16 +145,13 @@ local function uri_split(opts, cur_buf, cur_revspec)
         return
     end
 
-    local other_revspec
-    if cur.stage == 2 then
-        other_revspec = ":3:" .. cur.path
-    elseif cur.stage == 3 then
-        other_revspec = ":2:" .. cur.path
-    elseif cur.stage == 0 then
-        other_revspec = "HEAD:" .. cur.path
-    else
-        other_revspec = ":0:" .. cur.path
-    end
+    local mapping = {
+        [2] = { ":3:" .. cur.path, true },
+        [3] = { ":2:" .. cur.path, false },
+        [0] = { "HEAD:" .. cur.path, false },
+    }
+    local m = mapping[cur.stage] or { ":0:" .. cur.path, true }
+    local other_revspec, cur_left = m[1], m[2]
     local content = util.exec(
         { "git", "cat-file", "-p", other_revspec },
         { cwd = worktree, silent = true }
@@ -174,7 +163,7 @@ local function uri_split(opts, cur_buf, cur_revspec)
     place_pair(
         cur_buf,
         object.buf_for(worktree, other_revspec, content),
-        cur.stage ~= nil,
+        cur_left,
         opts.vertical
     )
 end
@@ -230,8 +219,8 @@ function M.split(opts)
     end
     local object = require("git.object")
     local buf = object.buf_for(worktree, revspec, content)
-    local other_writable = util.parse_revspec(revspec).stage == 0
-    place_pair(buf, cur_buf, other_writable, opts.vertical)
+    -- Revspec snapshot is older than the worktree, so it goes left.
+    place_pair(buf, cur_buf, true, opts.vertical)
 end
 
 return M