If possible, we should try not to use verbatim paths in Command::current_dir. It might work but it might also break code (including some Windows APIs) that assume the current directory isn't verbatim.
UEFI paths can be of 4 types:
1. Absolute Shell Path: Uses shell mappings
2. Absolute Device Path: this is what we want
3: Relative root: path relative to the current root.
4: Relative
Absolute shell path can be identified with `:` and Absolute Device path
can be identified with `/`. Relative root path will start with `\`.
The algorithm is mostly taken from edk2 UEFI shell implementation and is
somewhat simple. Check for the path type in order.
For Absolute Shell path, use `EFI_SHELL->GetDevicePathFromMap` to
get a BorrowedDevicePath for the volume.
For Relative paths, we use the current working directory to construct
the new path.
BorrowedDevicePath abstraction is needed to interact with
`EFI_SHELL->GetDevicePathFromMap` which returns a Device Path Protocol
with the lifetime of UEFI shell.
Absolute Shell paths cannot exist if UEFI shell is missing.
Signed-off-by: Ayush Singh <ayush@beagleboard.org>
I am working on fs support for UEFI [0], which similar to windows has prefix
components, but is not quite same as Windows. It also seems that Prefix
is tied closely to Windows and cannot really be extended [1].
This PR just tries to remove coupling between Prefix and absolute path
checking to allow platforms to provide there own implementation to check
if a path is absolute or not.
I am not sure if any platform other than windows currently uses Prefix,
so I have kept the path.prefix().is_some() check in most cases.
[0]: https://github.com/rust-lang/rust/pull/135368
[1]: https://github.com/rust-lang/rust/issues/52331#issuecomment-2492796137
Signed-off-by: Ayush Singh <ayush@beagleboard.org>
