Improve neovim config for git

- Only start in insert mode when editing a commit message (and not when
  doing a rebase or something else)
- Add colorcolumn to indicate maximum line length
- Add spell check

home-manager/modules/git.nix

@@ -13,7 +13,6 @@
       extraConfig = {
         init.defaultBranch = "main";
         core.pager = "${pkgs.diff-so-fancy}/bin/diff-so-fancy | less --tabs=4 -RFX";
-        core.editor = "${pkgs.neovim}/bin/nvim +star";
         diff.sops.textconv = "${pkgs.sops}/bin/sops -d";
         pull.ff = "only";
         alias.find-merge = "!sh -c 'commit=$0 && branch=\${1:-HEAD} && (git rev-list $commit..$branch --ancestry-path | cat -n; git rev-list $commit..$branch --first-parent | cat -n) | sort -k2 -s | uniq -f1 -d | sort -n | tail -1 | cut -f2'";

home-manager/modules/neovim.nix

@@ -43,6 +43,8 @@
           autocmd BufWinLeave * call clearmatches()
       augroup END
 
+      autocmd BufRead COMMIT_EDITMSG startinsert
+
       let g:deoplete#enable_at_startup = 1
 
       sign define LspDiagnosticsSignError text=🟥
@@ -183,4 +185,9 @@
       )
     )
   );
+
+  xdg.configFile."nvim/ftplugin/gitcommit.vim".text = ''
+    setlocal spell
+    setlocal colorcolumn=73
+  '';
 }