File/folder ignore using a file (similar to .gitignore mechanism)

[arc12]

Allowing users to use the "gitignore" mechanism could be useful - i.e allowing files (I'll call them ".ffsignore") to be placed anywhere in the filesystem which mark which folders/files should be ignored relative to the position of the .ffsignore file. This would be in addition to the current mechanism of specifying ignore information in FFS config.
Maybe .ffsignore would only apply to the source side of the comparison.

I believe there are several practical advantages to having this approach available:
- if folders containing .ffsignore files are moved then the ignore rules remain good.
- for some tasks, the user knows which files/folders should be ignored when creating then. This certainly applies when working with software code, e.g. when things are in a git repository. To be able to specify the ignore details at this time will be more reliable (less error prone) and less work than checking the FFS UI when running a sync.
- in cases where several FFS configurations are used over the same file system, it saves replicating ignore rules in multiple configurations. (I use different FFS sync models with different schedules to capture both history/changes and to maintain a true master).

Just an idea for a new feature, which I think would be helpful and could be easy to implement, given the existing logic.

Thanks for FFS!
Cheers, Adam