I can reproduce the issue and it will be fixed in next release.
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extfs: replace tmpfile if archive basefile has been changed
The current implementation was never really optimized for viewing large files and instead wastes a lot of memory for character lookup tables for faster preview. It can use 10 times the size of the file to view so it can crash on large files if not enough memory is available, or the system slow due to swapping. I will look into improving the memory usage.
support long file name
I have added support for longer names in e183f557566b2106d35f63e4f874c939eb7a91a7. It also fixes some other issues with the dirent struct and works around compiler warnings. Never actually tested it with longer names, so feedback is welcomed.
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tests: add a simple readdir test program