Add `default_current_dir()` function to `trycmd::cases::TestCases` to specify CWD

[ariasuni]

It doesn’t seem to be possible to set the CWD programmatically, like with e.g. std::process::Command in the stdlib.

My use case is that I want to handle fs operations myself (since I need to do some specific stuff with creation/modification/etc. dates, creating git repos, setting extended attributes on files, etc.), and set the CWD once for a group of tests instead of in every TOML file.

[epage]

Would be good to first explore what implications this might have on the design and how to deal with them. For example, I assume the user's current_dir would be the basis for the base of a step. What about if a step has fs.sandbox = true? Depending on the answer, how do we make this clear in the API?

[ariasuni]

There is already a fs.cwd that can be set in toml files. Maybe a default_current_dir() similar to default_bin_name() could be implemented? I don’t know about steps and fs.sandbox.

[epage]

That is a path relative to the fs.base