soundcloud/visor — pull request #53 by cloudhead (2012-07-18 15:53:55+00:00)
Title: Improve errors, scaling & files

- Implement NewError, to facilitate error handling/checking

- Implement IsErrNoEnt, to check for "file not found" errors

- Rename (*File).Update to 'Set'

Update was confusing, as the operation would succeed even if there
was no file at that path. Later, we will implement a real 'Update'
method.

- Move GetScale & SetScale to snapshot.go, as methods to Snapshot.

It is clearer what revision these functions will use, if they are
methods on Snapshot. Previously, GetScale used `nil` as the revision,
even though it took a Snapshot as argument.

- Implement GetScale using Files.

- Give the File type its own revision (FileRev)

...to distinguish from its Snapshot's revision. This allows the file
to be fast-forwarded without losing file revision information.