This modifies GCMemcard::TitlePresent() to match my findings of how the GC BIOS and various games behave when you alter the fields in the directory entry.
It looks like for a save to be recognized by a game, the following have to be true:
- Game code and maker code must exactly match what the game expects.
- Filename is only checked up to the first null byte. All bytes afterwards can be whatever.
The BIOS itself does a full compare of the filename when checking for whether it should allow copying a file from one card to another, but behaves oddly in some cases when there's non-null bytes after the first null. See the big comment in `HasSameIdentity()` for details.
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