NeogitLog: repeating entries

Description

After running :NeogitLog, once you have all history loaded, when you type + for "show more history", the log is appended to the existing list.

Neovim version

NVIM v0.11.2
Build type: Release
LuaJIT 2.1.1748459687

Operating system and version

Ubuntu 20.04.6 LTS on WSL2

Steps to reproduce

1. Open a file tracked by git
2. Run command :NeogitLog
3. Ensure all logs are shown
4. Note that the prompt for loading more history is still being shown
5. Type + to try and load more anyway
6. It will start back at the top and output to the log buffer

Expected behavior

• Message to load more is hidden when all history is displayed / reached the end of history
• If attempting to load more, do not append already-loaded history into the list

Actual behavior

• Message to load more is shown when all history has already been loaded
• Loading more after this point adds duplicates to the list

Start at the :NeogitLog entry point and trace how the + action requests another page after all history is loaded. Verify the end-of-history condition and the list update path; done means the load-more prompt disappears at the end and pressing + does not append duplicate entries.