Merge branch 'nd/builtin-to-libgit'

Code cleanups so that libgit.a does not depend on anything in the
builtin/ directory.

* nd/builtin-to-libgit:
  fetch-pack: move core code to libgit.a
  fetch-pack: remove global (static) configuration variable "args"
  send-pack: move core code to libgit.a
  Move setup_diff_pager to libgit.a
  Move print_commit_list to libgit.a
  Move estimate_bisect_steps to libgit.a
  Move try_merge_command and checkout_fast_forward to libgit.a

diff.c

@@ -4880,3 +4880,19 @@ size_t fill_textconv(struct userdiff_driver *driver,
 
 	return size;
 }
+
+void setup_diff_pager(struct diff_options *opt)
+{
+	/*
+	 * If the user asked for our exit code, then either they want --quiet
+	 * or --exit-code. We should definitely not bother with a pager in the
+	 * former case, as we will generate no output. Since we still properly
+	 * report our exit code even when a pager is run, we _could_ run a
+	 * pager with --exit-code. But since we have not done so historically,
+	 * and because it is easy to find people oneline advising "git diff
+	 * --exit-code" in hooks and other scripts, we do not do so.
+	 */
+	if (!DIFF_OPT_TST(opt, EXIT_WITH_STATUS) &&
+	    check_pager_config("diff") != 0)
+		setup_pager();
+}