There are different degrees of a cat being feral, and it will take different approaches before petting is an option. Be patient!
Most, if not all people, want to pet a feral cat when they see them. I have rescued hundreds of such cats. There are degrees of a cat being feral: very, partially (usually a domesticated cat the was dumped in a park, neighborhood, or section of woods recently), or a domesticated cat that got separated from their owner (and they are very scared). Some of these cats could have been abused too. It takes time to assess a feral cat.
The most important need for a cat is not self-gratification for the petting party but meeting the basic needs of the cat with food, water, shelter, and some time. I try to establish a regular schedule of feeding and conversation. If the cat doesn't have shelter, that too must be solved but that is another blog. The cat is looking for someone who has his best interest in mind. They must learn to trust again! Patience is necessary.
For instance, there is a feral cat by the name of Precious, I have been taking care of her for years. She has finally come forward to sniff a finger and to be touched lightly on the nose. It must be the cat's choice. Or take the cat Silver, who was dumped in a park and abused. But he found another feral cat named Sandy (whom I had been combing and petting) Silver saw that and came forward for the same.
You never know, but I'm positive God melts hearts just as He does for us. It is a supernatural experience on a small scale!