`File::close(self) -> std::io::Result<()>` for the `std`

[Byron]

Gitoxide shouldn't rely on File::drop() after writing files as it squelches errors. Instead, use io-close but push for the ability to close files to be added to the standard library.

Creating a PR for it would be the way to go.

[EliahKagan]

Are there places in gitoxide where the squelching of errors could be avoided, or meaningfully lessened, by doing an explicit flush before dropping a file that is open for write?

[Byron]

A quick search revealed that flush() is called in a couple of places already. It would also be a question if close() is necessarily flushing synchronously as well and thus would detect all possible errors - those related to flushing and those related to closing.
One might also think that flushing before closing (explicitly or implicitly) would always lure out errors related to the prior write.