P4 does not store the entire history locally, so your only limit is the amount of space on the server.
Git will pack objects after a while (initially they’re stored as-is, just compressed), but large files or enormous amounts of changes can make the repository grow to unwieldy amounts, and while git is able to perform “shallow” clones (clones which only store part of the history), not everything handles them well
Git also has "partial" clones, which can avoid some of the downsides of shallow clones. You can, for example, filter out all historical objects (--filter=blob:none). Historical objects are fetched lazily as needed, such as checking out an old revision. The same can be done with unreachable trees.
This article has excellent diagrams that depict the different types of clones:
Git will pack objects after a while (initially they’re stored as-is, just compressed), but large files or enormous amounts of changes can make the repository grow to unwieldy amounts, and while git is able to perform “shallow” clones (clones which only store part of the history), not everything handles them well