Apply Magento2 Patch manually using GIT

The best easy way is to simulate the directory path, so lets assume you will need to fix the comparison page after you upgrade to Magento 2.3.5-p2

Filename: vendor/magento/module-catalog/Helper/Output.php

we need to replace this line

- if (preg_match($pattern, $attributeHtml)) {

with this line

+ if (preg_match($pattern, (string) $attributeHtml)) {

Now create those directories vendor/magento/module-catalog/Helper

copy the file Output.php to that directory

create a copy from Output.php and rename it to OutputModified.php

do your changes (in our case it is only replace the above line) by this command

diff -u vendor/magento/module-catalog/Helper/Output.php vendor/magento/module-catalog/Helper/OutputModified.php > m2-hotfixes/your-fix.patch

after execute this command you will have the file your-fix.patch,

now open the patch and rename OutputModified.php with Output.php

and that's it now you can execute this to apply the patch

git apply m2-hotfixes/your-fix.patch

Note: you might need to open the patch and add "/" to the first of the paths

also you can ready here