option to override changesets from bookmark update log

Summary:
The sync job is usually just reading the bookmark update log but sometimes we
need it to pretend the contents are actually different to prevent it from
replicating problematic changes.

Reviewed By: RajivTS

Differential Revision: D55064423

fbshipit-source-id: 42e4e1fbc10ad7ce3a2ee6da9097ccec26cb48b3

eden/mononoke/mononoke_hg_sync_job/src/main.rs

@@ -412,6 +412,15 @@ impl HgSyncProcess {
                     .multiple(true)
                     .help("skip entries about particular bookmark from bookmark update log")
             )
+            .arg(
+                Arg::with_name("replace-changeset")
+                    .long("replace-changeset")
+                    .takes_value(true)
+                    .required(false)
+                    .multiple(true)
+                    .help("replace particular changeset mentioned in bookmark update log with a new commit hash, \
+                           the arg should be formatted like bonsai_csid:replacement_bonsai_csid")
+            )
             .arg(
                 Arg::with_name("combine-bundles")
                     .long("combine-bundles")
@@ -1384,6 +1393,18 @@ async fn run<'a>(
             let skip_bookmarks = sub_m
                 .values_of("skip-bookmark")
                 .map_or(Vec::new(), |v| v.collect());
+            let replace_changesets: HashMap<Option<ChangesetId>, Option<ChangesetId>> = sub_m
+                .values_of("replace-changeset")
+                .map_or(HashMap::new(), |v| {
+                    v.map(|cs_pair| {
+                        let mut split = cs_pair.split(':');
+                        (
+                            Some(split.next().unwrap().parse().unwrap()),
+                            Some(split.next().unwrap().parse().unwrap()),
+                        )
+                    })
+                    .collect()
+                });
             let loop_forever = sub_m.is_present("loop-forever");
             let replayed_sync_counter = LatestReplayedSyncCounter::new(
                 &repo,
@@ -1452,6 +1473,21 @@ async fn run<'a>(
                 entries
                     .into_iter()
                     .filter(|entry| !skip_bookmarks.contains(&entry.bookmark_name.as_str()))
+                    .map(|entry| {
+                        let from_changeset_id = replace_changesets
+                            .get(&entry.from_changeset_id)
+                            .cloned()
+                            .unwrap_or(entry.from_changeset_id);
+                        let to_changeset_id = replace_changesets
+                            .get(&entry.to_changeset_id)
+                            .cloned()
+                            .unwrap_or(entry.to_changeset_id);
+                        BookmarkUpdateLogEntry {
+                            from_changeset_id,
+                            to_changeset_id,
+                            ..entry
+                        }
+                    })
                     .collect::<Vec<_>>()
             })
             .fuse()