Make perf. run availability estimate more precise

Before, the estimation assumed that the newly queued commit always went to the end of the queue. However, in reality it might be positioned in an arbitrary place in the queue. Now its position in the queue is taken into account.

Author: Kobzol

site/src/github.rs

@@ -272,7 +272,7 @@ pub async fn enqueue_shas(
                 msg.push('\n');
             }
 
-            let artifacts_in_queue = ctxt.missing_commits().await.len();
+            let preceding_artifacts = count_preceding_in_queue(ctxt, &try_commit).await;
             let last_duration = conn
                 .last_artifact_collection()
                 .await
@@ -282,20 +282,17 @@ pub async fn enqueue_shas(
             // "Guess" that the duration will take about an hour if we don't have data or it's
             // suspiciously fast.
             let last_duration = last_duration.max(Duration::from_secs(3600));
+            // Also add the currently queued artifact to the duration
+            let expected_duration = (last_duration.as_secs() * (preceding_artifacts + 1)) as f64;
 
-            let expected_duration = (last_duration.as_secs() * artifacts_in_queue as u64) as f64;
-
-            // At this point, the queue should also contain the commit that we're mentioning below.
-            let other_artifact_count = artifacts_in_queue.saturating_sub(1);
-
-            let verb = if other_artifact_count == 1 {
+            let verb = if preceding_artifacts == 1 {
                 "is"
             } else {
                 "are"
             };
-            let suffix = if other_artifact_count == 1 { "" } else { "s" };
+            let suffix = if preceding_artifacts == 1 { "" } else { "s" };
             let queue_msg = format!(
-                r#"There {verb} currently {other_artifact_count} other artifact{suffix} in the [queue](https://perf.rust-lang.org/status.html).
+                r#"There {verb} currently {preceding_artifacts} other artifact{suffix} in the [queue](https://perf.rust-lang.org/status.html).
 It will probably take at least ~{:.1} hours until the benchmark run finishes."#,
                 (expected_duration / 3600.0)
             );
@@ -317,6 +314,15 @@ It will probably take at least ~{:.1} hours until the benchmark run finishes."#,
     Ok(())
 }
 
+/// Counts how many artifacts are in the queue before the specified commit.
+async fn count_preceding_in_queue(ctxt: &SiteCtxt, commit: &TryCommit) -> u64 {
+    let queue = ctxt.missing_commits().await;
+    queue
+        .iter()
+        .position(|(c, _)| c.sha == commit.sha())
+        .unwrap_or(queue.len()) as u64
+}
+
 #[derive(Debug, Deserialize)]
 #[serde(tag = "type")]
 enum HomuComment {