heroku: Add and use commit() fn with fallback logic

Use `HEROKU_BUILD_COMMIT` first, falling back to `HEROKU_SLUG_COMMIT`
for backward compatibility with deployments using the older
`runtime-dyno-metadata` Labs feature.

Author: Turbo87

crates/crates_io_database_dump/src/lib.rs

@@ -70,7 +70,7 @@ impl DumpDirectory {
         }
         let metadata = Metadata {
             timestamp: &self.timestamp,
-            crates_io_commit: crates_io_heroku::slug_commit()
+            crates_io_commit: crates_io_heroku::commit()
                 .ok()
                 .flatten()
                 .unwrap_or_else(|| "unknown".to_owned()),

crates/crates_io_heroku/src/lib.rs

@@ -2,6 +2,42 @@
 
 use crates_io_env_vars::var;
 
+/// Returns the Git SHA of the currently deployed commit.
+///
+/// This function tries `HEROKU_BUILD_COMMIT` first (the current standard),
+/// and falls back to `HEROKU_SLUG_COMMIT` (deprecated) if the former is not
+/// set. This provides compatibility with both old and new Heroku deployments.
+///
+/// Both environment variables are set by Heroku when the appropriate Labs
+/// features are enabled (`runtime-dyno-build-metadata` for `HEROKU_BUILD_COMMIT`,
+/// `runtime-dyno-metadata` for `HEROKU_SLUG_COMMIT`).
+///
+/// Returns `None` if neither variable is set (e.g., in local development).
+///
+/// See <https://devcenter.heroku.com/articles/dyno-metadata> for more
+/// information.
+///
+/// # Examples
+///
+/// ```
+/// use crates_io_heroku::commit;
+///
+/// if let Ok(Some(commit)) = commit() {
+///     println!("Running commit: {}", commit);
+/// } else {
+///     println!("Commit SHA unknown");
+/// }
+/// ```
+pub fn commit() -> anyhow::Result<Option<String>> {
+    // Try the current standard first
+    if let Some(commit) = build_commit()? {
+        return Ok(Some(commit));
+    }
+
+    // Fall back to the deprecated variable for backward compatibility
+    slug_commit()
+}
+
 /// Returns the Git SHA of the currently deployed commit.
 ///
 /// This value comes from the `HEROKU_SLUG_COMMIT` environment variable,

src/config/sentry.rs

@@ -1,6 +1,6 @@
 use anyhow::Context;
 use crates_io_env_vars::{required_var, var, var_parsed};
-use crates_io_heroku::slug_commit;
+use crates_io_heroku::commit;
 use sentry::IntoDsn;
 use sentry::types::Dsn;
 
@@ -29,7 +29,7 @@ impl SentryConfig {
         Ok(Self {
             dsn,
             environment,
-            release: slug_commit()?,
+            release: commit()?,
             traces_sample_rate: var_parsed("SENTRY_TRACES_SAMPLE_RATE")?.unwrap_or(0.0),
         })
     }

src/controllers/site_metadata.rs

@@ -1,7 +1,7 @@
 use crate::app::AppState;
 use axum::Json;
 use axum::response::IntoResponse;
-use crates_io_heroku::slug_commit;
+use crates_io_heroku::commit;
 use serde::Serialize;
 
 #[derive(Debug, Serialize, utoipa::ToSchema)]
@@ -34,7 +34,7 @@ pub struct MetadataResponse<'a> {
 pub async fn get_site_metadata(state: AppState) -> impl IntoResponse {
     let read_only = state.config.db.are_all_read_only();
 
-    let deployed_sha = slug_commit().ok().flatten();
+    let deployed_sha = commit().ok().flatten();
     let deployed_sha = deployed_sha.as_deref().unwrap_or("unknown");
 
     Json(MetadataResponse {