add an useful File::append() utility

[liigo]

// open an existing or create a new file for append data.
// very useful when writing log files.

pub fn append<P: AsRef<Path>>(path: P) -> io::Result<File> {
    OpenOptions::new().append(true).create(true).open(path.as_ref())
}

• open_append() doesn't make sense, since it maybe creates new file
• create_append() doesn't make sense, since it maybe open existing file

Since we‘re adding open_buffered and create_buffered, I think we also have a chance to add File::append. File::options().append(true).create(true).open(path.as_ref()) is too long and requires thinking more on flags in detail.

[jieyouxu]

Hi @liigo thanks for the feature request. This is an API request, so you should instead open an API Change Proposal (ACP) at https://github.com/rust-lang/libs-team/issues.

[liigo]

@jieyouxu ACP link: rust-lang/libs-team#512

[jieyouxu]

Thanks! I'm going to close this issue on the rust-lang/rust side in favor of rust-lang/libs-team#512, since this is not actionable for this issue tracker.