Allow running an arbitrary number of try jobs per PR

src/ci/citool/src/jobs.rs

@@ -271,7 +271,11 @@ pub enum RunType {
     /// Workflows that run after a push to a PR branch
     PullRequest,
     /// Try run started with @bors try
-    TryJob { job_patterns: Option<Vec<String>> },
+    TryJob {
+        job_patterns: Option<Vec<String>>,
+        /// Should the limit on the number of try jobs be ignored?
+        nolimit: bool,
+    },
     /// Merge attempt workflow
     AutoJob,
     /// Fake job only used for sharing Github Actions cache.
@@ -289,7 +293,7 @@ fn calculate_jobs(
 ) -> anyhow::Result<Vec<GithubActionsJob>> {
     let (jobs, prefix, base_env) = match run_type {
         RunType::PullRequest => (db.pr_jobs.clone(), "PR", &db.envs.pr_env),
-        RunType::TryJob { job_patterns } => {
+        RunType::TryJob { job_patterns, nolimit } => {
             let jobs = if let Some(patterns) = job_patterns {
                 let mut jobs: Vec<Job> = vec![];
                 let mut unknown_patterns = vec![];
@@ -311,7 +315,7 @@ fn calculate_jobs(
                         unknown_patterns.join(", ")
                     ));
                 }
-                if jobs.len() > MAX_TRY_JOBS_COUNT {
+                if jobs.len() > MAX_TRY_JOBS_COUNT && !nolimit {
                     return Err(anyhow::anyhow!(
                         "It is only possible to schedule up to {MAX_TRY_JOBS_COUNT} custom jobs, received {} custom jobs expanded from {} pattern(s)",
                         jobs.len(),
@@ -342,7 +346,7 @@ fn calculate_jobs(
             // built toolchain using `rustup-toolchain-install-master`),
             // we inject the `DIST_TRY_BUILD` environment variable to the jobs
             // to tell `opt-dist` to make the build faster by skipping certain steps.
-            if let RunType::TryJob { job_patterns } = run_type {
+            if let RunType::TryJob { job_patterns, nolimit: _ } = run_type {
                 if job_patterns.is_none() {
                     env.insert(
                         "DIST_TRY_BUILD".to_string(),

src/ci/citool/src/main.rs

@@ -30,6 +30,12 @@ const CI_DIRECTORY: &str = concat!(env!("CARGO_MANIFEST_DIR"), "/..");
 pub const DOCKER_DIRECTORY: &str = concat!(env!("CARGO_MANIFEST_DIR"), "/../docker");
 const JOBS_YML_PATH: &str = concat!(env!("CARGO_MANIFEST_DIR"), "/../github-actions/jobs.yml");
 
+#[derive(Default)]
+struct TryJobMetadata {
+    job_patterns: Vec<String>,
+    nolimit: bool,
+}
+
 struct GitHubContext {
     event_name: String,
     branch_ref: String,
@@ -41,38 +47,63 @@ impl GitHubContext {
         match (self.event_name.as_str(), self.branch_ref.as_str()) {
             ("pull_request", _) => Some(RunType::PullRequest),
             ("push", "refs/heads/automation/bors/try-perf" | "refs/heads/try-perf") => {
-                Some(RunType::TryJob { job_patterns: None })
+                Some(RunType::TryJob { job_patterns: None, nolimit: false })
             }
             ("push", "refs/heads/automation/bors/try") => {
-                let patterns = self.get_try_job_patterns();
-                let patterns = if !patterns.is_empty() { Some(patterns) } else { None };
-                Some(RunType::TryJob { job_patterns: patterns })
+                let metadata = self.get_try_job_metadata();
+                let patterns = if !metadata.job_patterns.is_empty() {
+                    Some(metadata.job_patterns)
+                } else {
+                    None
+                };
+                Some(RunType::TryJob { job_patterns: patterns, nolimit: metadata.nolimit })
             }
             ("push", "refs/heads/automation/bors/auto") => Some(RunType::AutoJob),
             ("push", "refs/heads/main") => Some(RunType::MainJob),
             _ => None,
         }
     }
 
-    /// Tries to parse patterns of CI jobs that should be executed
-    /// from the commit message of the passed GitHub context
+    /// Tries to parse metadata about try jobs from the commit message.
+    ///
+    /// Currently, two things can be specified.
+    ///
+    /// # Try job patterns
+    /// The first is a set of patterns of CI jobs that should be executed.
     ///
     /// They can be specified in the form of
     /// try-job: <job-pattern>
     /// or
     /// try-job: `<job-pattern>`
     /// (to avoid GitHub rendering the glob patterns as Markdown)
-    fn get_try_job_patterns(&self) -> Vec<String> {
-        if let Some(ref msg) = self.commit_message {
-            msg.lines()
-                .filter_map(|line| line.trim().strip_prefix("try-job: "))
-                // Strip backticks if present
-                .map(|l| l.trim_matches('`'))
-                .map(|l| l.trim().to_string())
-                .collect()
-        } else {
-            vec![]
+    ///
+    /// # No limit
+    /// The second is a marker that specifies that the limit on the maximum number of allowed try
+    /// jobs to execute should NOT be applied.
+    ///
+    /// try-nolimit
+    fn get_try_job_metadata(&self) -> TryJobMetadata {
+        let Some(commit_msg) = &self.commit_message else {
+            return TryJobMetadata::default();
+        };
+
+        let mut nolimit = false;
+        let mut job_patterns = vec![];
+
+        for line in commit_msg.lines() {
+            let line = line.trim();
+            if line.starts_with("try-nolimit") {
+                nolimit = true;
+                continue;
+            }
+            let Some(pattern) = line.strip_prefix("try-job: ") else {
+                continue;
+            };
+            // Strip backticks if present
+            let pattern = pattern.trim_matches('`');
+            job_patterns.push(pattern.trim().to_string());
         }
+        TryJobMetadata { job_patterns, nolimit }
     }
 }