fix(git): reset diff-pair cursor on sidebar selection

lua/git/status_view.lua

@@ -404,7 +404,10 @@ local function view_row(s, row, focus_left)
             mods = { vertical = true },
         })
         left_win = vim.api.nvim_get_current_win()
+        vim.api.nvim_win_set_cursor(left_win, { 1, 0 })
+        vim.api.nvim_win_set_cursor(target, { 1, 0 })
     end)
+    ---@cast left_win -nil
     vim.api.nvim_set_current_win(focus_left and left_win or status_win)
 end
 

test/git/status_view_test.lua

@@ -405,3 +405,83 @@ t.test("sidebar buffer name does not get written to disk", function()
         "no real file should be created at the sidebar buffer's path"
     )
 end)
+
+t.test(
+    "diffsplit from sidebar resets cursor so panes stay in sync",
+    function()
+        local committed, worktree = {}, {}
+        for i = 1, 100 do
+            committed[i] = "line " .. i
+            worktree[i] = i == 10
+                    and "CHANGED " .. i
+                or i == 40 and "CHANGED " .. i
+                or i == 70 and "CHANGED " .. i
+                or i == 90 and "CHANGED " .. i
+                or ("line " .. i)
+        end
+        local repo = h.make_repo({
+            ["file.txt"] = table.concat(committed, "\n") .. "\n",
+        })
+        t.write(repo, "file.txt", table.concat(worktree, "\n") .. "\n")
+        vim.cmd("cd " .. repo)
+
+        -- Open the worktree file in a normal window and position cursor in
+        -- what becomes a folded section after diff is set up.
+        vim.cmd("edit file.txt")
+        vim.api.nvim_win_set_cursor(0, { 50, 0 })
+
+        require("git.status_view").open({ placement = "sidebar" })
+        local sidebar_buf, sidebar_win = find_sidebar()
+        assert(sidebar_buf and sidebar_win)
+        local r = assert(require("git.core.repo").find(vim.fn.getcwd()))
+        r:refresh()
+        t.wait_for(function()
+            return r.status and #r.status:rows("unstaged") > 0
+        end, "git status to report unstaged changes")
+
+        local entry_line
+        for i, l in
+            ipairs(vim.api.nvim_buf_get_lines(sidebar_buf, 0, -1, false))
+        do
+            if l:match("file.txt$") then
+                entry_line = i
+                break
+            end
+        end
+        if not entry_line then
+            error("entry line should exist")
+        end
+
+        vim.api.nvim_set_current_win(sidebar_win)
+        vim.api.nvim_win_set_cursor(sidebar_win, { entry_line, 0 })
+        t.press("<Tab>")
+        t.wait_for(function()
+            return find_diff_win("left") ~= nil
+                and find_diff_win("right") ~= nil
+        end, "diff pair to appear")
+
+        local left_win = assert(find_diff_win("left"))
+        local right_win = assert(find_diff_win("right"))
+        local left_top =
+            vim.api.nvim_win_call(left_win, function() return vim.fn.line("w0") end)
+        local right_top = vim.api.nvim_win_call(
+            right_win,
+            function() return vim.fn.line("w0") end
+        )
+        t.eq(
+            left_top,
+            right_top,
+            "left and right panes should have the same topline after diffsplit"
+        )
+        t.eq(
+            vim.api.nvim_win_get_cursor(left_win),
+            { 1, 0 },
+            "left pane should start at line 1"
+        )
+        t.eq(
+            vim.api.nvim_win_get_cursor(right_win),
+            { 1, 0 },
+            "right pane should start at line 1"
+        )
+    end
+)