Refactoring

[kyazdani42]

Doing:

• use vim nightly features
• when updating file system, check for open buffers, if some name matches, change the buffer names to avoid conflicts when saving a file
• fix various bugs
• use fs_scandir instead of ls which makes ignoring also available on macos and makes the tree much much much faster

not doing:

• bufferize project in the background to open directories faster -> too slow
• whole tree async with luv fs operations -> codebase becomes messy