Merge branch 'jk/common-main'

There are certain house-keeping tasks that need to be performed at
the very beginning of any Git program, and programs that are not
built-in commands had to do them exactly the same way as "git"
potty does.  It was easy to make mistakes in one-off standalone
programs (like test helpers).  A common "main()" function that
calls cmd_main() of individual program has been introduced to
make it harder to make mistakes.

* jk/common-main:
  mingw: declare main()'s argv as const
  common-main: call git_setup_gettext()
  common-main: call restore_sigpipe_to_default()
  common-main: call sanitize_stdfds()
  common-main: call git_extract_argv0_path()
  add an extra level of indirection to main()

t/helper/test-config.c

@@ -66,7 +66,7 @@ static int iterate_cb(const char *var, const char *value, void *data)
 	return 0;
 }
 
-int main(int argc, char **argv)
+int cmd_main(int argc, const char **argv)
 {
 	int i, val;
 	const char *v;