feat(src/msg.rs): allow logging to stderr in AdminLog — radicle-ci-broker

Signed-off-by: Lars Wirzenius liw@liw.fi

     pub struct AdminLog {
         filename: Option<PathBuf>,
         file: Option<File>,
         stderr: bool,
     }
     impl AdminLog {
         /// Create an admin log that doesn't write to a file, but to
         /// stderr.
         /// Create an admin log that doesn't write to a file, and
         /// neither to stderr.
         pub fn null() -> Self {
             Self::default()
         }
         /// Create an admin log that writes to stderr.
         pub fn stderr() -> Self {
             Self {
                 filename: None,
                 file: None,
                 stderr: true,
             }
         }
         /// Create an admin log that writes to a named file.
         pub fn open(filename: &Path) -> Result<Self, LogError> {
             let file = OpenOptions::new()

             Ok(Self {
                 filename: Some(filename.into()),
                 file: Some(file),
                 stderr: false,
             })
         }

                 #[allow(clippy::unwrap_used)] // we know it's OK
                 file.write_all(msg.as_bytes())
                     .map_err(|e| LogError::WriteLogFile(self.filename.clone().unwrap(), e))?;
             } else if self.stderr {
                 std::io::stderr()
                     .write_all(msg.as_bytes())
                     .map_err(LogError::WriteLogStderr)?;
             }
             Ok(())
         }

         #[error("failed to write to log file {0}")]
         WriteLogFile(PathBuf, #[source] std::io::Error),
         /// Can't write to file.
         #[error("failed to write to log file {0}")]
         WriteLogStderr(#[source] std::io::Error),
         /// Can' format time stamp.
         #[error("failed to format time stamp")]
         TimeFormat(#[source] time::error::Format),