Generalisation: copy gridfiles

[ZedThree]

Am I right in thinking that we also need to deal with copying any other files/data into the target directory here? I know we don't usually have anything else in a BOUT++ data dir but it's possible we might want to copy in grid files etc. (if we're trying to run lots of jobs in parallel there could be issues trying to access netcdf grid files from different processes at once?)

Originally posted by @d7919 in #2 (comment)

Possible solution: add self.additional_setup to BOUTEncoder.encode, defaults to no-op?

[bendudson]

We could have an optional grid file argument to the encoder. If that's set, then perhaps copy (or link) in the target directory, and set the BOUT.inp file mesh:file key to the necessary path. The trouble is that this should be the relative path from where the run is launched, rather than the relative path from the BOUT.inp file (which may have been a mistake...)