tig: prefer git that's in PATH over the bundled one (#489353)

pkgs/by-name/ti/tig/package.nix

@@ -73,8 +73,9 @@ stdenv.mkDerivation (finalAttrs: {
     # ZSH can be used (Completion/Unix/Command/_git: "_tig () { _git-log }"):
     #install -D contrib/tig-completion.zsh $out/share/zsh/site-functions/_tig
 
+    # Prefer the git in PATH, but add a fallback one in case there isn't one.
     wrapProgram $out/bin/tig \
-      --prefix PATH ':' "${git}/bin"
+      --suffix PATH ':' "${git}/bin"
   '';
 
   outputs = [