From 6a86a75ed5ecf6061e97389e8a7d6acc56279747 Mon Sep 17 00:00:00 2001
From: Oscar Wallberg <oscar.wallberg@outlook.com>
Date: Mon, 27 Apr 2026 16:02:14 +0200
Subject: [PATCH] refactor(git): convert blocking subprocess calls to async

---
 lua/git/cmd.lua        |  63 +++++++++++----------
 lua/git/commit.lua     |  34 ++++++-----
 lua/git/diff.lua       |  79 +++++++++++++++-----------
 lua/git/init.lua       |  27 +++++++++
 lua/git/log_win.lua    |  55 +++++++++---------
 lua/git/repo.lua       | 100 ++++++++++++++++-----------------
 lua/git/show.lua       | 109 ++++++++++++++++++++++--------------
 lua/git/status_win.lua | 124 ++++++++++++++++++++---------------------
 8 files changed, 338 insertions(+), 253 deletions(-)

diff --git a/lua/git/cmd.lua b/lua/git/cmd.lua
index 91b94e4..27864ec 100644
--- a/lua/git/cmd.lua
+++ b/lua/git/cmd.lua
@@ -1,3 +1,4 @@
+local git = require("git")
 local log = require("log")
 local repo = require("git.repo")
 local util = require("util")
@@ -39,11 +40,7 @@ local function prefetch_cmds()
     vim.system(
         { "git", "--list-cmds=main,others,alias" },
         { text = true },
-        function(result)
-            vim.schedule(function()
-                populate_cached_cmds(result)
-            end)
-        end
+        vim.schedule_wrap(populate_cached_cmds)
     )
 end
 
@@ -75,33 +72,41 @@ end
 ---@param args string[]
 ---@param conf ow.Git.SplitHandler
 local function run_in_split(worktree, args, conf)
-    vim.cmd("new")
-    local buf = vim.api.nvim_get_current_buf()
-    vim.bo[buf].buftype = "nofile"
-    vim.bo[buf].bufhidden = "hide"
-    vim.bo[buf].swapfile = false
-    vim.bo[buf].modifiable = false
+    local buf = git.new_scratch()
     vim.b[buf].git_worktree = worktree
     if conf.needs_ref then
         local user_ref = first_positional(args, 2) or "HEAD"
-        local sha = repo.rev_parse(worktree, user_ref, true)
-        if sha then
-            vim.b[buf].git_ref = sha
-            vim.b[buf].git_parent_ref =
-                repo.rev_parse(worktree, user_ref .. "^", true)
+        local function apply_name(label)
+            if not vim.api.nvim_buf_is_valid(buf) then
+                return
+            end
+            pcall(vim.api.nvim_buf_set_name, buf, "git://" .. label .. "/")
+            vim.bo[buf].filetype = conf.ft
         end
-        pcall(
-            vim.api.nvim_buf_set_name,
-            buf,
-            "git://" .. (sha or user_ref) .. "/"
-        )
+        repo.rev_parse(worktree, user_ref, true, function(sha)
+            if not sha then
+                apply_name(user_ref)
+                return
+            end
+            repo.rev_parse(worktree, user_ref .. "^", true, function(parent)
+                if not vim.api.nvim_buf_is_valid(buf) then
+                    return
+                end
+                vim.b[buf].git_ref = sha
+                vim.b[buf].git_parent_ref = parent
+                apply_name(sha)
+            end)
+        end)
+    else
+        vim.bo[buf].filetype = conf.ft
     end
-    vim.bo[buf].filetype = conf.ft
 
     local cmd = { "git" }
     vim.list_extend(cmd, args)
-    vim.system(cmd, { cwd = worktree, text = true }, function(obj)
-        vim.schedule(function()
+    vim.system(
+        cmd,
+        { cwd = worktree, text = true },
+        vim.schedule_wrap(function(obj)
             if not vim.api.nvim_buf_is_valid(buf) then
                 return
             end
@@ -124,7 +129,7 @@ local function run_in_split(worktree, args, conf)
                 )
             end
         end)
-    end)
+    )
 end
 
 ---@param worktree string
@@ -132,8 +137,10 @@ end
 local function run_to_messages(worktree, args)
     local cmd = { "git" }
     vim.list_extend(cmd, args)
-    vim.system(cmd, { cwd = worktree, text = true }, function(obj)
-        vim.schedule(function()
+    vim.system(
+        cmd,
+        { cwd = worktree, text = true },
+        vim.schedule_wrap(function(obj)
             local out = vim.trim(obj.stdout or "")
             local err = vim.trim(obj.stderr or "")
             local chunks = {}
@@ -156,7 +163,7 @@ local function run_to_messages(worktree, args)
                 vim.api.nvim_echo(chunks, true, {})
             end
         end)
-    end)
+    )
 end
 
 ---@param args string[]
diff --git a/lua/git/commit.lua b/lua/git/commit.lua
index ebccde1..fd74343 100644
--- a/lua/git/commit.lua
+++ b/lua/git/commit.lua
@@ -67,20 +67,26 @@ function M.commit(opts)
             if amend then
                 table.insert(cmd, "--amend")
             end
-            local result = vim.system(cmd, { cwd = worktree, text = true })
-                :wait()
-            if result.code ~= 0 then
-                log.error(
-                    "git commit failed: %s",
-                    vim.trim(result.stderr or "")
-                )
-                return
-            end
-            local out = vim.trim(result.stdout or "")
-            if out ~= "" then
-                log.info("%s", out)
-            end
-            vim.api.nvim_buf_delete(buf, { force = true })
+            vim.system(
+                cmd,
+                { cwd = worktree, text = true },
+                vim.schedule_wrap(function(result)
+                    if result.code ~= 0 then
+                        log.error(
+                            "git commit failed: %s",
+                            vim.trim(result.stderr or "")
+                        )
+                        return
+                    end
+                    local out = vim.trim(result.stdout or "")
+                    if out ~= "" then
+                        log.info("%s", out)
+                    end
+                    if vim.api.nvim_buf_is_valid(buf) then
+                        vim.api.nvim_buf_delete(buf, { force = true })
+                    end
+                end)
+            )
         end,
     })
 end
diff --git a/lua/git/diff.lua b/lua/git/diff.lua
index 6374fc6..89f1607 100644
--- a/lua/git/diff.lua
+++ b/lua/git/diff.lua
@@ -59,47 +59,62 @@ local function attach_index_writer(buf, worktree, path)
     })
 end
 
+---Run `git show <revspec>` asynchronously and call `callback(lines?)` on the
+---main loop. `lines` is nil on failure (the error is logged).
 ---@param worktree string
 ---@param revspec string  anything `git show` accepts (e.g. `HEAD:foo`, `:foo`, blob SHA)
----@return string[]
-local function read_show(worktree, revspec)
-    local result = vim.system(
+---@param callback fun(lines: string[]?)
+local function read_show_async(worktree, revspec, callback)
+    vim.system(
         { "git", "show", revspec },
-        { cwd = worktree, text = true }
+        { cwd = worktree, text = true },
+        vim.schedule_wrap(function(result)
+            if result.code ~= 0 then
+                log.error(
+                    "git show %s failed: %s",
+                    revspec,
+                    vim.trim(result.stderr or "")
+                )
+                callback(nil)
+                return
+            end
+            callback(util.split_lines(result.stdout or ""))
+        end)
     )
-        :wait()
-    if result.code ~= 0 then
-        log.error(
-            "git show %s failed: %s",
-            revspec,
-            vim.trim(result.stderr or "")
-        )
-        return {}
-    end
-    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`.
+---Internal builder: create a scratch buffer immediately and asynchronously
+---fill it with the content of `git show <revspec>`. Returning the buffer
+---synchronously lets callers wire up windows / `:diffthis` right away; the
+---diff updates when the content arrives. The buffer starts non-modifiable
+---and the index `BufWriteCmd` is only attached after a successful load, so
+---a premature `:w` can't blow away the index entry with empty content.
 ---@param worktree string
 ---@param revspec string
 ---@param is_index boolean
 ---@param index_path string?  required when is_index is true
 ---@return integer
 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].buftype = "nofile"
     vim.bo[buf].bufhidden = "wipe"
     vim.bo[buf].swapfile = false
-    if is_index then
-        attach_index_writer(buf, worktree, assert(index_path))
-    else
-        vim.bo[buf].modifiable = false
-    end
+    vim.bo[buf].modifiable = false
     vim.bo[buf].modified = false
+    read_show_async(worktree, revspec, function(lines)
+        if not vim.api.nvim_buf_is_valid(buf) then
+            return
+        end
+        vim.bo[buf].modifiable = true
+        vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines or {})
+        if is_index then
+            vim.bo[buf].buftype = "acwrite"
+            attach_index_writer(buf, worktree, assert(index_path))
+        else
+            vim.bo[buf].modifiable = false
+        end
+        vim.bo[buf].modified = false
+    end)
     return buf
 end
 
@@ -192,12 +207,14 @@ function M.split(opts)
     local label = is_index and "index" or opts.ref
     M.set_buf_name_and_filetype(other, "git://" .. label .. "/" .. rel)
 
-    local split_cmd = opts.vertical and "leftabove vertical sbuffer "
-        or "leftabove sbuffer "
-    vim.cmd(split_cmd .. other)
-    vim.cmd("diffthis")
-    vim.cmd("wincmd p")
-    vim.cmd("diffthis")
+    local cur_win = vim.api.nvim_get_current_win()
+    local other_win = vim.api.nvim_open_win(other, true, {
+        split = opts.vertical and "left" or "above",
+        win = cur_win,
+    })
+    vim.wo[other_win].diff = true
+    vim.api.nvim_set_current_win(cur_win)
+    vim.wo[cur_win].diff = true
 end
 
 return M
diff --git a/lua/git/init.lua b/lua/git/init.lua
index 4af5f42..b9a8bc2 100644
--- a/lua/git/init.lua
+++ b/lua/git/init.lua
@@ -25,6 +25,33 @@ function M.head(path)
     return repo.head(path)
 end
 
+---@class ow.Git.NewScratchOpts
+---@field name string?
+---@field bufhidden ("hide"|"wipe")?  defaults to "hide"
+---@field split ("above"|"below"|"left"|"right")?  defaults to splitbelow-aware horizontal
+
+---Open a split with a fresh non-modifiable scratch buffer. Default split
+---direction is horizontal, honouring `splitbelow`. Caller flips
+---`modifiable`, fills the buffer, and sets `filetype` once content lands.
+---@param opts ow.Git.NewScratchOpts?
+---@return integer buf
+---@return integer win
+function M.new_scratch(opts)
+    opts = opts or {}
+    local buf = vim.api.nvim_create_buf(false, true)
+    vim.bo[buf].buftype = "nofile"
+    vim.bo[buf].bufhidden = opts.bufhidden or "hide"
+    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
+    local split = opts.split or (vim.o.splitbelow and "below" or "above")
+    local win = vim.api.nvim_open_win(buf, true, { split = split })
+    return buf, win
+end
+
 function M.setup()
     for name, link in pairs(HIGHLIGHTS) do
         vim.api.nvim_set_hl(0, name, { link = link, default = true })
diff --git a/lua/git/log_win.lua b/lua/git/log_win.lua
index ac4f321..3ea68c1 100644
--- a/lua/git/log_win.lua
+++ b/lua/git/log_win.lua
@@ -1,3 +1,4 @@
+local git = require("git")
 local log = require("log")
 local repo = require("git.repo")
 local util = require("util")
@@ -13,32 +14,36 @@ function M.show()
         return
     end
 
-    local result = vim.system({
-        "git",
-        "log",
-        "--graph",
-        "--all",
-        "--decorate",
-        "--date=short",
-        "--format=format:" .. LOG_FORMAT,
-    }, { cwd = worktree, text = true }):wait()
-    if result.code ~= 0 then
-        log.error("git log failed: %s", result.stderr or "")
-        return
-    end
-
-    local lines = util.split_lines(result.stdout or "")
-
-    vim.cmd("new")
-    local buf = vim.api.nvim_get_current_buf()
-    vim.bo[buf].buftype = "nofile"
-    vim.bo[buf].bufhidden = "hide"
-    vim.bo[buf].swapfile = false
-    vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
-    vim.bo[buf].modifiable = false
-    vim.bo[buf].modified = false
+    local buf = git.new_scratch()
     vim.b[buf].git_worktree = worktree
-    vim.bo[buf].filetype = "gitlog"
+
+    vim.system(
+        {
+            "git",
+            "log",
+            "--graph",
+            "--all",
+            "--decorate",
+            "--date=short",
+            "--format=format:" .. LOG_FORMAT,
+        },
+        { cwd = worktree, text = true },
+        vim.schedule_wrap(function(result)
+            if not vim.api.nvim_buf_is_valid(buf) then
+                return
+            end
+            if result.code ~= 0 then
+                log.error("git log failed: %s", vim.trim(result.stderr or ""))
+                return
+            end
+            local lines = util.split_lines(result.stdout or "")
+            vim.bo[buf].modifiable = true
+            vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
+            vim.bo[buf].modifiable = false
+            vim.bo[buf].modified = false
+            vim.bo[buf].filetype = "gitlog"
+        end)
+    )
 end
 
 return M
diff --git a/lua/git/repo.lua b/lua/git/repo.lua
index 20cfe29..b2dca0c 100644
--- a/lua/git/repo.lua
+++ b/lua/git/repo.lua
@@ -1,7 +1,9 @@
 local log = require("log")
 local util = require("util")
 
-local UNMERGED = {
+local M = {}
+
+M.UNMERGED = {
     DD = true,
     AU = true,
     UD = true,
@@ -14,7 +16,7 @@ local UNMERGED = {
 ---@param code string porcelain v1 XY code
 ---@return string? char
 ---@return string? hl_group
-local function indicator(code)
+function M.indicator(code)
     if code == "" then
         return nil
     end
@@ -24,7 +26,7 @@ local function indicator(code)
     if code == "!!" then
         return "!", "GitIgnored"
     end
-    if UNMERGED[code] then
+    if M.UNMERGED[code] then
         return "U", "GitUnmerged"
     end
     local x, y = code:sub(1, 1), code:sub(2, 2)
@@ -43,7 +45,7 @@ end
 ---@param code string
 ---@return string?
 local function format(code)
-    local char, hl = indicator(code)
+    local char, hl = M.indicator(code)
     if not char then
         return nil
     end
@@ -53,7 +55,7 @@ end
 ---@param path string
 ---@return string? gitdir
 ---@return string? worktree
-local function resolve(path)
+function M.resolve(path)
     local found = vim.fs.find(".git", { upward = true, path = path })[1]
     if not found then
         return nil
@@ -88,12 +90,12 @@ end
 ---both when not inside a git repo.
 ---@return string? gitdir
 ---@return string? worktree
-local function resolve_cwd()
+function M.resolve_cwd()
     local path = vim.api.nvim_buf_get_name(0)
     if path == "" then
         path = vim.fn.getcwd()
     end
-    return resolve(path)
+    return M.resolve(path)
 end
 
 ---@class ow.Git.Repo
@@ -152,15 +154,17 @@ local function do_refresh(repo)
     -- path lines, so it ignores `##` lines below. Running with `--branch`
     -- lets the sidebar reuse this single subprocess via the GitRefresh
     -- data payload instead of spawning its own.
-    vim.system({
-        "git",
-        "-c",
-        "core.quotePath=false",
-        "status",
-        "--porcelain=v1",
-        "--branch",
-    }, { cwd = repo.worktree, text = true }, function(obj)
-        vim.schedule(function()
+    vim.system(
+        {
+            "git",
+            "-c",
+            "core.quotePath=false",
+            "status",
+            "--porcelain=v1",
+            "--branch",
+        },
+        { cwd = repo.worktree, text = true },
+        vim.schedule_wrap(function(obj)
             local statuses = {}
             if obj.code == 0 then
                 for line in (obj.stdout or ""):gmatch("[^\r\n]+") do
@@ -210,7 +214,7 @@ local function do_refresh(repo)
                 },
             })
         end)
-    end)
+    )
 end
 
 ---@param gitdir string
@@ -244,7 +248,7 @@ local function register(buf)
     if path == "" then
         return nil
     end
-    local gitdir, worktree = resolve(path)
+    local gitdir, worktree = M.resolve(path)
     if not gitdir or not worktree then
         return nil
     end
@@ -259,7 +263,7 @@ local function register(buf)
 end
 
 ---@param buf integer
-local function unregister(buf)
+function M.unregister(buf)
     local repo = repo_by_buf[buf]
     if not repo then
         return
@@ -273,7 +277,7 @@ local function unregister(buf)
 end
 
 ---@param buf integer
-local function refresh_buf(buf)
+function M.refresh_buf(buf)
     if not vim.api.nvim_buf_is_valid(buf) or vim.bo[buf].buftype ~= "" then
         return
     end
@@ -285,7 +289,7 @@ local function refresh_buf(buf)
     repo:refresh()
 end
 
-local function stop_all()
+function M.stop_all()
     for _, repo in pairs(repo_by_gitdir) do
         repo:stop_watcher()
     end
@@ -293,8 +297,8 @@ end
 
 ---@param path string
 ---@return string?
-local function head(path)
-    local gitdir = resolve(path)
+function M.head(path)
+    local gitdir = M.resolve(path)
     if not gitdir then
         return nil
     end
@@ -318,39 +322,35 @@ local function head(path)
     return nil
 end
 
----Resolve a git revision to its object SHA. Returns nil if the ref can't be
----resolved (root-commit's `^`, blob's `^`, malformed ref, etc.). When `short`
----is true, the result is abbreviated via `core.abbrev` (auto-extended by git
----to keep the prefix unique in the current repo).
+---Resolve a git revision to its object SHA. Calls `callback(sha?)` on the
+---main loop with nil if the ref can't be parsed (root-commit's `^`, blob's
+---`^`, malformed ref, etc.). When `short` is true, the result is abbreviated
+---via `core.abbrev` (auto-extended by git to keep the prefix unique in the
+---current repo).
 ---@param worktree string
 ---@param ref string
----@param short? boolean
----@return string?
-local function rev_parse(worktree, ref, short)
+---@param short boolean
+---@param callback fun(sha: string?)
+function M.rev_parse(worktree, ref, short, callback)
     local cmd = { "git", "rev-parse", "--verify", "--quiet" }
     if short then
         table.insert(cmd, "--short")
     end
     table.insert(cmd, ref)
-    local result = vim.system(cmd, { cwd = worktree, text = true }):wait()
-    if result.code ~= 0 then
-        return nil
-    end
-    local sha = vim.trim(result.stdout or "")
-    if sha == "" then
-        return nil
-    end
-    return sha
+    vim.system(
+        cmd,
+        { cwd = worktree, text = true },
+        vim.schedule_wrap(function(result)
+            local sha
+            if result.code == 0 then
+                local trimmed = vim.trim(result.stdout or "")
+                if trimmed ~= "" then
+                    sha = trimmed
+                end
+            end
+            callback(sha)
+        end)
+    )
 end
 
-return {
-    UNMERGED = UNMERGED,
-    head = head,
-    indicator = indicator,
-    refresh_buf = refresh_buf,
-    resolve = resolve,
-    resolve_cwd = resolve_cwd,
-    rev_parse = rev_parse,
-    stop_all = stop_all,
-    unregister = unregister,
-}
+return M
diff --git a/lua/git/show.lua b/lua/git/show.lua
index 05ed999..c8bb916 100644
--- a/lua/git/show.lua
+++ b/lua/git/show.lua
@@ -1,4 +1,5 @@
 local diff = require("git.diff")
+local git = require("git")
 local log = require("log")
 local repo = require("git.repo")
 local util = require("util")
@@ -111,8 +112,8 @@ end
 ---@param ref string
 local function show_blob(worktree, blob, path, ref)
     local buf = blob_buf(worktree, blob, path, ref)
-    vim.cmd("normal! m'")
-    vim.cmd("buffer " .. buf)
+    vim.cmd.normal({ "m'", bang = true })
+    vim.api.nvim_set_current_buf(buf)
 end
 
 ---@param ctx ow.Git.ShowContext
@@ -127,53 +128,75 @@ local function show_diff(ctx, section)
         blob_buf(ctx.worktree, section.pre_blob, section.pre_path, parent)
     local right =
         blob_buf(ctx.worktree, section.post_blob, section.post_path, ctx.ref)
-    vim.cmd("normal! m'")
-    vim.cmd("buffer " .. left)
-    vim.cmd("diffthis")
-    vim.cmd("rightbelow vertical sbuffer " .. right)
-    vim.cmd("diffthis")
-    vim.cmd("wincmd p")
+    vim.cmd.normal({ "m'", bang = true })
+    local left_win = vim.api.nvim_get_current_win()
+    vim.api.nvim_set_current_buf(left)
+    vim.wo[left_win].diff = true
+    local right_win =
+        vim.api.nvim_open_win(right, true, { split = "right", win = left_win })
+    vim.wo[right_win].diff = true
+    vim.api.nvim_set_current_win(left_win)
 end
 
 ---@param worktree string
 ---@param ref string
 function M.open_commit(worktree, ref)
-    local sha = repo.rev_parse(worktree, ref, true) or ref
-    local name = "git://" .. sha .. "/"
-    -- Reuse a previously-opened buffer for the same commit; commit SHAs
-    -- 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.cmd("normal! m'")
-        vim.cmd("buffer " .. existing)
-        return
-    end
+    repo.rev_parse(worktree, ref, true, function(resolved)
+        local sha = resolved or ref
+        local name = "git://" .. sha .. "/"
+        -- Reuse a previously-opened buffer for the same commit; commit SHAs
+        -- 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",
+            })
+            return
+        end
 
-    local result = vim.system(
-        { "git", "show", ref },
-        { cwd = worktree, text = true }
-    )
-        :wait()
-    if result.code ~= 0 then
-        log.error("git show %s failed: %s", ref, result.stderr or "")
-        return
-    end
-    local lines = util.split_lines(result.stdout or "")
-    local parent = repo.rev_parse(worktree, ref .. "^", true)
-    local buf = vim.api.nvim_create_buf(false, true)
-    vim.bo[buf].buftype = "nofile"
-    vim.bo[buf].bufhidden = "hide"
-    vim.bo[buf].swapfile = false
-    vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
-    vim.bo[buf].modifiable = false
-    vim.bo[buf].modified = false
-    pcall(vim.api.nvim_buf_set_name, buf, name)
-    vim.b[buf].git_worktree = worktree
-    vim.b[buf].git_ref = sha
-    vim.b[buf].git_parent_ref = parent
-    vim.bo[buf].filetype = "git"
-    vim.cmd("normal! m'")
-    vim.cmd("buffer " .. buf)
+        local buf, win = git.new_scratch({ name = name })
+        vim.b[buf].git_worktree = worktree
+        vim.b[buf].git_ref = sha
+
+        vim.system(
+            { "git", "show", ref },
+            { cwd = worktree, text = true },
+            vim.schedule_wrap(function(result)
+                if result.code ~= 0 then
+                    log.error(
+                        "git show %s failed: %s",
+                        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
+                        pcall(vim.api.nvim_win_close, win, true)
+                    end
+                    if vim.api.nvim_buf_is_valid(buf) then
+                        pcall(vim.api.nvim_buf_delete, buf, { force = true })
+                    end
+                    return
+                end
+                if not vim.api.nvim_buf_is_valid(buf) then
+                    return
+                end
+                local lines = util.split_lines(result.stdout or "")
+                repo.rev_parse(worktree, ref .. "^", true, function(parent)
+                    if not vim.api.nvim_buf_is_valid(buf) then
+                        return
+                    end
+                    vim.b[buf].git_parent_ref = parent
+                    vim.bo[buf].modifiable = true
+                    vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
+                    vim.bo[buf].modifiable = false
+                    vim.bo[buf].modified = false
+                    vim.bo[buf].filetype = "git"
+                end)
+            end)
+        )
+    end)
 end
 
 ---@return boolean dispatched true if the cursor was on an actionable line
diff --git a/lua/git/status_win.lua b/lua/git/status_win.lua
index e45a142..375eb16 100644
--- a/lua/git/status_win.lua
+++ b/lua/git/status_win.lua
@@ -1,4 +1,5 @@
 local diff = require("git.diff")
+local git = require("git")
 local log = require("log")
 local repo = require("git.repo")
 
@@ -240,13 +241,15 @@ local function enrich_with_log(worktree, branch, groups, callback)
     end
     local pending = #fetches
     for _, f in ipairs(fetches) do
-        vim.system({
-            "git",
-            "log",
-            "--format=%h %s",
-            f.range,
-        }, { cwd = worktree, text = true }, function(log_obj)
-            vim.schedule(function()
+        vim.system(
+            {
+                "git",
+                "log",
+                "--format=%h %s",
+                f.range,
+            },
+            { cwd = worktree, text = true },
+            vim.schedule_wrap(function(log_obj)
                 if log_obj.code == 0 then
                     for line in (log_obj.stdout or ""):gmatch("[^\r\n]+") do
                         local sha, subject = line:match("^(%S+)%s+(.+)$")
@@ -270,7 +273,7 @@ local function enrich_with_log(worktree, branch, groups, callback)
                     callback(branch, groups)
                 end
             end)
-        end)
+        )
     end
 end
 
@@ -287,15 +290,17 @@ local function fetch_status(worktree, prefetched_stdout, callback)
         enrich_with_log(worktree, branch, groups, callback)
         return
     end
-    vim.system({
-        "git",
-        "-c",
-        "core.quotePath=false",
-        "status",
-        "--porcelain=v1",
-        "--branch",
-    }, { cwd = worktree, text = true }, function(obj)
-        vim.schedule(function()
+    vim.system(
+        {
+            "git",
+            "-c",
+            "core.quotePath=false",
+            "status",
+            "--porcelain=v1",
+            "--branch",
+        },
+        { cwd = worktree, text = true },
+        vim.schedule_wrap(function(obj)
             if obj.code ~= 0 then
                 log.error("git status failed: %s", vim.trim(obj.stderr or ""))
                 local branch = { ahead = 0, behind = 0 }
@@ -313,7 +318,7 @@ local function fetch_status(worktree, prefetched_stdout, callback)
             local branch, groups = parse_porcelain(obj.stdout or "")
             enrich_with_log(worktree, branch, groups, callback)
         end)
-    end)
+    )
 end
 
 ---@param bufnr integer
@@ -598,9 +603,7 @@ end
 ---@param win integer
 ---@param enabled boolean
 local function set_diff(win, enabled)
-    vim.api.nvim_win_call(win, function()
-        vim.cmd(enabled and "diffthis" or "diffoff")
-    end)
+    vim.wo[win].diff = enabled
     if enabled then
         vim.wo[win].foldenable = true
         vim.wo[win].foldlevel = 0
@@ -642,6 +645,21 @@ local function entry_key(entry)
     return entry.section .. "|" .. entry.path .. "|" .. (entry.orig or "")
 end
 
+---Split `target_win` and put its buffer into the new window. Matches the
+---semantics of `:set_current_win(target); :rightbelow/leftabove vertical
+---split` (the new window inherits the target's buffer; caller swaps it
+---afterwards via `nvim_win_set_buf`).
+---@param target_win integer
+---@param dir "left"|"right"
+---@return integer
+local function vsplit_at(target_win, dir)
+    return vim.api.nvim_open_win(
+        vim.api.nvim_win_get_buf(target_win),
+        true,
+        { split = dir, win = target_win }
+    )
+end
+
 ---@param s ow.Git.StatusState
 ---@param entry ow.Git.StatusEntry
 ---@param focus_left boolean
@@ -673,23 +691,17 @@ local function show_diff(s, entry, focus_left)
     end
 
     if left_win and not right_win then
-        vim.api.nvim_set_current_win(left_win)
-        vim.cmd("rightbelow vertical split")
-        right_win = vim.api.nvim_get_current_win()
+        right_win = vsplit_at(left_win, "right")
         reset_diff_win(right_win)
     elseif right_win and not left_win then
-        vim.api.nvim_set_current_win(right_win)
-        vim.cmd("leftabove vertical split")
-        left_win = vim.api.nvim_get_current_win()
+        left_win = vsplit_at(right_win, "left")
         reset_diff_win(left_win)
     elseif not (left_win or right_win) then
         local default_main = find_default_main_win(sidebar_win)
         if default_main then
             right_win = default_main
             reset_diff_win(right_win)
-            vim.api.nvim_set_current_win(default_main)
-            vim.cmd("leftabove vertical split")
-            left_win = vim.api.nvim_get_current_win()
+            left_win = vsplit_at(right_win, "left")
             reset_diff_win(left_win)
         else
             -- No reusable default-empty window. Open the diff pair by
@@ -697,12 +709,9 @@ local function show_diff(s, entry, focus_left)
             -- when there are other windows to absorb the split; if the
             -- sidebar is the only window in the tab, the split has to take
             -- from the sidebar itself, so restore the width explicitly.
-            vim.api.nvim_set_current_win(sidebar_win)
-            vim.cmd("rightbelow vertical split")
-            right_win = vim.api.nvim_get_current_win()
+            right_win = vsplit_at(sidebar_win, "right")
             reset_diff_win(right_win)
-            vim.cmd("leftabove vertical split")
-            left_win = vim.api.nvim_get_current_win()
+            left_win = vsplit_at(right_win, "left")
             reset_diff_win(left_win)
             vim.api.nvim_win_set_width(sidebar_win, SIDEBAR_WIDTH)
         end
@@ -756,13 +765,11 @@ local function action_stage()
     vim.system(
         { "git", "add", "--", entry.path },
         { cwd = s.worktree },
-        function(obj)
+        vim.schedule_wrap(function(obj)
             if obj.code ~= 0 then
-                vim.schedule(function()
-                    log.error("git add failed: %s", vim.trim(obj.stderr or ""))
-                end)
+                log.error("git add failed: %s", vim.trim(obj.stderr or ""))
             end
-        end
+        end)
     )
 end
 
@@ -780,16 +787,18 @@ local function action_unstage()
         table.insert(cmd, entry.orig)
     end
     table.insert(cmd, entry.path)
-    vim.system(cmd, { cwd = s.worktree }, function(obj)
-        if obj.code ~= 0 then
-            vim.schedule(function()
+    vim.system(
+        cmd,
+        { cwd = s.worktree },
+        vim.schedule_wrap(function(obj)
+            if obj.code ~= 0 then
                 log.error(
                     "git restore --staged failed: %s",
                     vim.trim(obj.stderr or "")
                 )
-            end)
-        end
-    end)
+            end
+        end)
+    )
 end
 
 local function action_discard()
@@ -828,16 +837,14 @@ local function action_discard()
             vim.system(
                 { "git", "checkout", "--", entry.path },
                 { cwd = s.worktree },
-                function(obj)
+                vim.schedule_wrap(function(obj)
                     if obj.code ~= 0 then
-                        vim.schedule(function()
-                            log.error(
-                                "git checkout failed: %s",
-                                vim.trim(obj.stderr or "")
-                            )
-                        end)
+                        log.error(
+                            "git checkout failed: %s",
+                            vim.trim(obj.stderr or "")
+                        )
                     end
-                end
+                end)
             )
         end
     else
@@ -875,15 +882,8 @@ local function open(worktree)
     end
 
     local previous_win = vim.api.nvim_get_current_win()
-    vim.cmd("leftabove vertical new")
-    local win = vim.api.nvim_get_current_win()
-    local bufnr = vim.api.nvim_get_current_buf()
-
-    vim.bo[bufnr].buftype = "nofile"
-    vim.bo[bufnr].bufhidden = "wipe"
-    vim.bo[bufnr].swapfile = false
+    local bufnr, win = git.new_scratch({ split = "left", bufhidden = "wipe" })
     vim.bo[bufnr].filetype = "gitstatus"
-    vim.bo[bufnr].modifiable = false
 
     vim.wo[win].number = false
     vim.wo[win].relativenumber = false