add high level description about changes in borgbackup compared to attic

[ThomasWaldmann]

• in general: lots of tickets from attic issue tracker fixed (bugs, features), see Dealing with attic issues #5 for a list
• less chunk management overhead (less memory and disk usage) via adjustable chunker params
• faster remote cache resync (useful when backing up multiple machines into same repo)
• compression: lz4 and lzma compression, adjustable compression levels
• better error messages / exception handling
• repokey replaces problematic passphrase mode (you can't change the passphrase nor the pbkdf2 iteration count in "passphrase" mode)
• simple sparse file support
• can read special files (e.g. block devices) or stdin directly
• mkdir-based locking is more compatible than attic's posix locking
• tested on misc. linux systems, 32 and 64bit, freebsd, openbsd, netbsd, mac os x
• use fadvise to not spoil / blow up the cache
• better output for verbose mode, progress indication

[anarcat]

any more details on:

repokey replaces problematic passphrase mode

didn't see this one pass by...

where should this be documented? FAQ?

[ThomasWaldmann]

Maybe a section in the README.rst.

[anarcat]

hmm... i don't know, there's already a lot of stuff in there... there's already a section about Attic in the FAQ, i think that would be a better place.