git: avoid calling aliased builtins via their dashed form

This is one of the few places where Git violates its own deprecation of
the dashed form. It is not necessary, either.

As of 595d59e2b5 (git.c: ignore pager.* when launching builtin as
dashed external, 2017-08-02), Git wants to ignore the pager.* config
setting when expanding aliases. So let's strip out the
check_pager_config(<command-name>) call from the copy-edited code.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

git.c

@@ -699,6 +699,31 @@ static int run_argv(int *argcp, const char ***argv)
 		 */
 		if (!done_alias)
 			handle_builtin(*argcp, *argv);
+		else if (get_builtin(**argv)) {
+			struct argv_array args = ARGV_ARRAY_INIT;
+			int i;
+
+			if (get_super_prefix())
+				die("%s doesn't support --super-prefix", **argv);
+
+			commit_pager_choice();
+
+			argv_array_push(&args, "git");
+			for (i = 0; i < *argcp; i++)
+				argv_array_push(&args, (*argv)[i]);
+
+			trace_argv_printf(args.argv, "trace: exec:");
+
+			/*
+			 * if we fail because the command is not found, it is
+			 * OK to return. Otherwise, we just pass along the status code.
+			 */
+			i = run_command_v_opt(args.argv, RUN_SILENT_EXEC_FAILURE |
+					      RUN_CLEAN_ON_EXIT);
+			if (i >= 0 || errno != ENOENT)
+				exit(i);
+			die("could not execute builtin %s", **argv);
+		}
 
 		/* .. then try the external ones */
 		execv_dashed_external(*argv);