[Evangelical]

This "theory" about Adam repenting or not repenting sounds a lot like OBW recently said about Witness Lee "... taught a lot of things that were nowhere in the text. The were just his opinions.".

Let's consider the facts of what the bible actually says.

It says that instead of repenting, the first thing they did was hide from God and cover themselves up. They tried to hide their sin and cover it, not repent.

God is gracious towards them but this is likely due to His grace and mercy and not dependent upon their repentance. A person could construct an equally plausible theory about Adam and Eve's repentance:
God showed them grace and mercy despite them not having repented. Perhaps their feeling of guilt and regret as evidenced by them hiding from God and covering themselves, was enough for God to show mercy.

God covering them with sheepskin is to show God covering their sin, His grace and mercy, irrespective of whether they repented or not (they were saved by grace, not works).

We should keep in mind that the bible never mentions anything about Adam or Eve's repentance because the point of the story of Adam and Eve's transgression is to show us that all men have sinned, to point to Christ.