message: Set a minimum for last-modified in sitemap
  This should encourage Google to recrawl pages that now use the /latest/
  URLs and have canonicalization links.
diff: @@ -6,7 +6,7 @@ use crate::{
  web::error::Nope,
  web::page::WebPage,
  };
  -use chrono::{DateTime, Utc};
  +use chrono::{DateTime, TimeZone, Utc};
  use iron::{
  headers::ContentType,
  mime::{Mime, SubLevel, TopLevel},
  @@ -86,6 +86,9 @@ pub fn sitemap_handler(req: &mut Request) -> IronResult<Response> {
  target_name: row.get("target_name"),
  last_modified: row
  .get::<_, DateTime<Utc>>("release_time")
  + // On Aug 27 2022 we added `<link rel="canonical">` to all pages,
  + // so they should all get recrawled if they haven't been since then.
  + .max(Utc.ymd(2022, 8, 28).and_hms(0, 0, 0))
  .format("%+")
  .to_string(),
  })
  @@ -227,6 +230,26 @@ mod tests {
  })
  }
  + #[test]
  + fn sitemap_max_age() {
  + wrapper(|env| {
  + let web = env.frontend();
  +
  + use chrono::{TimeZone, Utc};
  + env.fake_release()
  + .name("some_random_crate")
  + .release_time(Utc.ymd(2020, 1, 1).and_hms(0, 0, 0))
  + .create()?;
  +
  + let response = web.get("/-/sitemap/s/sitemap.xml").send()?;
  + assert!(response.status().is_success());
  +
  + let content = response.text()?;
  + assert!(content.contains(&"2022-08-28T00:00:00+00:00"));
  + Ok(())
  + })
  + }
  +
  #[test]
  fn about_page() {
  wrapper(|env| {
  