fix: another case of incorrect alternate buffers (#60)

lua/oil/init.lua

@@ -405,6 +405,7 @@ M.select = function(opts)
       vertical = opts.vertical,
       horizontal = opts.horizontal,
       split = opts.split,
+      keepalt = true,
     }
     if vim.tbl_isempty(mods) then
       mods = nil

lua/oil/util.lua

@@ -102,11 +102,16 @@ M.rename_buffer = function(src_bufnr, dest_buf_name)
   -- rename logic. The only reason we can't use nvim_buf_set_name on files is because vim will
   -- think that the new buffer conflicts with the file next time it tries to save.
   if not vim.loop.fs_stat(dest_buf_name) then
+    local altbuf = vim.fn.bufnr("#")
     -- This will fail if the dest buf name already exists
     local ok = pcall(vim.api.nvim_buf_set_name, src_bufnr, dest_buf_name)
     if ok then
       -- Renaming the buffer creates a new buffer with the old name. Find it and delete it.
       vim.api.nvim_buf_delete(vim.fn.bufadd(bufname), {})
+      if altbuf and vim.api.nvim_buf_is_valid(altbuf) then
+        vim.fn.setreg("#", altbuf)
+      end
+
       return false
     end
   end

tests/altbuf_spec.lua

@@ -81,6 +81,30 @@ a.describe("Alternate buffer", function()
     assert.equals("bar", vim.fn.expand("#"))
   end)
 
+  a.it("preserves alternate when traversing oil dirs", function()
+    vim.cmd.edit({ args = { "foo" } })
+    oil.open()
+    test_util.wait_for_autocmd("BufReadPost")
+    a.util.sleep(10)
+    assert.equals("foo", vim.fn.expand("#"))
+    vim.api.nvim_win_set_cursor(0, { 1, 1 })
+    oil.select()
+    test_util.wait_for_autocmd("BufReadPost")
+    assert.equals("foo", vim.fn.expand("#"))
+  end)
+
+  a.it("preserves alternate when opening preview", function()
+    vim.cmd.edit({ args = { "foo" } })
+    oil.open()
+    test_util.wait_for_autocmd("BufReadPost")
+    a.util.sleep(10)
+    assert.equals("foo", vim.fn.expand("#"))
+    vim.api.nvim_win_set_cursor(0, { 1, 1 })
+    oil.select({ preview = true })
+    test_util.wait_for_autocmd("BufReadPost")
+    assert.equals("foo", vim.fn.expand("#"))
+  end)
+
   a.describe("floating window", function()
     a.it("sets previous buffer as alternate", function()
       vim.cmd.edit({ args = { "foo" } })