Add support for sync.com

[tillydray]

#1761

Add support for Sync.com. Probably not mergeable though because you said, "If [nested symlinks are] not supported, I would not support this officially, because people tend to blame the last element in the chain for losing their file, and Mackup is usually it."

I did this work anyway because 1) I was curious and bored 😄 2) I didn't grok what you said until I was halfway through.

All submissions

• I have followed the Contributing Guidelines
• I have checked to ensure there aren't other open Pull Requests for the same update/change

Adding/updating Application X Support

N/A

Improving the Mackup codebase

I wasn't able to run the tests because pyenv install 3.7.4 was failing 😕

• My submission passes the tests
• I have linted the code locally prior to submission
• I have written new tests as applicable
• I have added an explanation of what the changes do

[spuder]

I'm so excited for sync.com support since its exactly what dropbox was 10 years ago.

Could you elaborate on what you mean about nested symlinks? They appear to work for me, but maybe I am not understanding correctly.

touch /tmp/foo.txt      # Create a file on disk at /tmp
echo '42' > /tmp/foo.txt      # Add some data to that file
ln -s /tmp/foo.txt ~/Sync/foo.txt       # Symlink from the local disk to Sync folder
ln -s ~/Sync.foo.txt ~/Sync/bar.txt      # Create a 'nested' symlink that points to another symlink
cat ~/Sync/bar.txt      # Follow 2 layers of symlinks
42      # Observe 2 layers of symlinks are readable

[tillydray]

Could you elaborate on what you mean about nested symlinks? They appear to work for me

sync.com‘s official stance is that nested symlinks may not work. They also appear to work for me, and have for a couple months. At this point I am entrusting some important things to nested symlinks actually working. 😬

[tillydray]

@spuder you can see the original discussion with official links here #1760