refactor(diffsplit): clarify diff side API

test/git/diffsplit_test.lua

@@ -0,0 +1,129 @@
+local Revision = require("git.core.revision")
+local h = require("test.git.helpers")
+local t = require("test")
+
+---@return integer[]
+local function diff_wins()
+    local wins = {}
+    for _, win in ipairs(vim.api.nvim_tabpage_list_wins(0)) do
+        if vim.wo[win].diff then
+            table.insert(wins, win)
+        end
+    end
+    return wins
+end
+
+---@param role "left"|"right"
+---@return integer
+local function vertical_diff_win(role)
+    local wins = diff_wins()
+    table.sort(wins, function(a, b)
+        return vim.api.nvim_win_get_position(a)[2]
+            < vim.api.nvim_win_get_position(b)[2]
+    end)
+    local win = role == "left" and wins[1] or wins[#wins]
+    if not win then
+        error("diff window not found")
+    end
+    return win
+end
+
+---@param dir string
+local function cleanup_dir_buffers(dir)
+    for _, buf in ipairs(vim.api.nvim_list_bufs()) do
+        local name = vim.api.nvim_buf_get_name(buf)
+        if name:find(dir, 1, true) then
+            pcall(vim.api.nvim_buf_delete, buf, { force = true })
+        end
+    end
+end
+
+t.test("open from worktree focuses the index pane", function()
+    local dir = h.make_repo({ ["a.txt"] = "old\n" })
+    t.write(dir, "a.txt", "new\n")
+    vim.cmd.edit(vim.fs.joinpath(dir, "a.txt"))
+
+    local current_buf = vim.api.nvim_get_current_buf()
+    require("git.diffsplit").open()
+
+    t.wait_for(function()
+        return #diff_wins() == 2
+    end, "diff windows to open")
+
+    t.eq(vim.api.nvim_get_current_win(), vertical_diff_win("left"))
+    t.truthy(
+        vim.api.nvim_get_current_buf() ~= current_buf,
+        "worktree buffer should lose focus"
+    )
+end)
+
+t.test("open from index focuses the worktree pane", function()
+    local dir = h.make_repo({ ["a.txt"] = "old\n" })
+    t.write(dir, "a.txt", "new\n")
+    local r = assert(require("git.core.repo").resolve(dir))
+    local index_buf = require("git.object").buf_for(
+        r,
+        Revision.new({ stage = 0, path = "a.txt" })
+    )
+    vim.api.nvim_set_current_buf(index_buf)
+
+    require("git.diffsplit").open({ layout = "vertical" })
+
+    t.wait_for(function()
+        return #diff_wins() == 2
+    end, "diff windows to open")
+
+    local right = vertical_diff_win("right")
+    t.eq(
+        vim.api.nvim_get_current_win(),
+        right,
+        "worktree buffer should be focused"
+    )
+    t.truthy(
+        vim.api.nvim_get_current_buf() ~= index_buf,
+        "index buffer should lose focus"
+    )
+end)
+
+t.test("open_pair keeps old on the left when splitright is set", function()
+    local dir = vim.fn.tempname()
+    vim.fn.mkdir(dir, "p")
+    t.defer(function()
+        cleanup_dir_buffers(dir)
+        vim.fn.delete(dir, "rf")
+    end)
+
+    local old = vim.fs.joinpath(dir, "old.txt")
+    local new = vim.fs.joinpath(dir, "new.txt")
+    vim.fn.writefile({ "old" }, old)
+    vim.fn.writefile({ "new" }, new)
+
+    local prev_splitright = vim.o.splitright
+    vim.o.splitright = true
+    t.defer(function()
+        vim.o.splitright = prev_splitright
+    end)
+
+    local old_buf = vim.fn.bufadd(old)
+    local new_buf = vim.fn.bufadd(new)
+    vim.fn.bufload(old_buf)
+    vim.fn.bufload(new_buf)
+
+    require("git.diffsplit").open_pair(old_buf, new_buf, {
+        layout = "vertical",
+    })
+
+    t.wait_for(function()
+        return #diff_wins() == 2
+    end, "diff windows to open")
+
+    local left = vertical_diff_win("left")
+    local right = vertical_diff_win("right")
+    t.eq(vim.api.nvim_win_get_buf(left), old_buf, "old pane should be left")
+    t.eq(vim.api.nvim_win_get_buf(right), new_buf, "new pane should be right")
+    t.eq(
+        vim.api.nvim_get_current_win(),
+        right,
+        "new pane should be focused by default"
+    )
+end)