For me patching always results in errors. A while ago it worked very smoothly, but since 1.35 I cannot use it any more. Just tried to patch a 1.39.5 to 1.39.6
Hunk #1 succeeded at 6 with fuzz 2. Hunk #2 succeeded at 24 (offset 6 lines). Hunk #3 FAILED at 43. Hunk #4 FAILED at 494. Hunk #5 FAILED at 535. Hunk #6 succeeded at 4073 with fuzz 2 (offset 3465 lines). 3 out of 6 hunks FAILED checking file vendor/composer/autoload_files.php Hunk #1 FAILED at 10. 1 out of 1 hunk FAILED checking file vendor/composer/autoload_psr4.php Hunk #1 FAILED at 28. 1 out of 1 hunk FAILED checking file vendor/composer/autoload_real.php Reversed (or previously applied) patch detected! Assume -R? [n]