fix: cwd not set upon loading first buffer

[Subjective]

Problem: Normally, <c-g> and :w will output a message with the current buffer's filename relative the the cwd. However, when the buffer is restored from a session, the message (as well as the default statusline) show the filename relative the home directory instead. This doesn't seem to happen in tab-scoped sessions where each tab has its own cwd.

Before saving session (cwd set to ~/Documents):

After restoring session:

In the "after" screenshot, the cwd is set correctly, but the filename is displayed as if it were set to the home directory.

Solution: This PR resolves the issue by setting global options upon loading the first buffer. It also uses the lua api to set the cwd instead of vim.cmd.

[stevearc]

This doesn't feel like the right way to do this. If the first buffer in the restore list was unloaded, then we will never restore the global options.

Could this be fixed by just adding another

if not data.tab_scoped then
  vim.api.nvim_set_current_dir(data.global.cwd)
end

after the tabs and buffers are all restored?

[Subjective]

Yeah nvm, I found an edgecase where if one of the buffers in the restore list is not under the cwd, then the relative file path does not show correctly for all the subsequent buffers, even those buffers are under the cwd. Removing the check for the first buffer fixes this, but it feels redundant to repeatedly set global options for each buffer.

I'll try out your suggestion

[Subjective]

@stevearc setting the cwd again after loading all buffers/tabs seems to work

[stevearc]

Thanks for the PR!