diff --git a/cmdlib/src/args.rs b/cmdlib/src/args.rs
index d71d5603af..e9ad4c99cd 100644
--- a/cmdlib/src/args.rs
+++ b/cmdlib/src/args.rs
@@ -760,13 +760,7 @@ pub fn get_usize<'a>(matches: &ArgMatches<'a>, key: &str, default: usize) -> usi
 
 #[inline]
 pub fn get_u64<'a>(matches: &ArgMatches<'a>, key: &str, default: u64) -> u64 {
-    matches
-        .value_of(key)
-        .map(|val| {
-            val.parse::<u64>()
-                .expect(&format!("{} must be integer", key))
-        })
-        .unwrap_or(default)
+    get_u64_opt(matches, key).unwrap_or(default)
 }
 
 #[inline]
@@ -777,15 +771,17 @@ pub fn get_u64_opt<'a>(matches: &ArgMatches<'a>, key: &str) -> Option<u64> {
     })
 }
 
+#[inline]
+pub fn get_i32_opt<'a>(matches: &ArgMatches<'a>, key: &str) -> Option<i32> {
+    matches.value_of(key).map(|val| {
+        val.parse::<i32>()
+            .expect(&format!("{} must be integer", key))
+    })
+}
+
 #[inline]
 pub fn get_i32<'a>(matches: &ArgMatches<'a>, key: &str, default: i32) -> i32 {
-    matches
-        .value_of(key)
-        .map(|val| {
-            val.parse::<i32>()
-                .expect(&format!("{} must be integer", key))
-        })
-        .unwrap_or(default)
+    get_i32_opt(matches, key).unwrap_or(default)
 }
 
 #[inline]
diff --git a/tests/integration/commitsyncmap.toml b/tests/integration/commitsyncmap.toml
new file mode 100644
index 0000000000..e25fa0c0d7
--- /dev/null
+++ b/tests/integration/commitsyncmap.toml
@@ -0,0 +1,46 @@
+# Common definition for commit sync path mapping
+#
+# A top-level config must have a name and a repo-id of a large repo
+# It may have multiple subconfigs, named `<top-level-name>.small_repos`
+# Each of the the `small_repos` configs MUST have:
+# - a repo id
+# - a bookmark prefix to prepend to every bookmark name
+# - a default path syncing action. Is used when none of the
+#   "map" values matches a path. Can be one of:
+#   - "preserve": keep this path as it is when syncing
+#   - "prepend_prefix": prepend the "default_prefix" to this path
+#      when syncing
+# Each of the `small_repos` configs MAY have:
+# - a map of prefixes to new prefixes, key "map"
+#
+# Note: config is written from the "bottom-up" perspective, e.g.
+#       it contains mappings, needed to sync small repos into a
+#       a large repo. This mapping needs to be reversable
+#       (and is reversed when the sync happens in a large-to-small
+#       direction)
+
+[megarepo_test]
+large_repo_id = 0
+direction = "small_to_large"
+common_pushrebase_bookmarks = ["master"]
+
+    [[megarepo_test.small_repos]]
+    repoid = 1
+    bookmark_prefix = "fbsource"
+    default_action = "preserve"
+
+        [megarepo_test.small_repos.map]
+        "arvr" = ".fbsource-rest/arvr"
+
+    [[megarepo_test.small_repos]]
+    repoid = 2
+    bookmark_prefix = "ovrsource"
+    default_action = "prepend_prefix"
+    default_prefix = "arvr-legacy"
+
+        [megarepo_test.small_repos.map]
+        "arvr" = "arvr"
+        "fbcode" = ".ovrsource-rest/fbcode"
+        "fbandroid" = ".ovrsource-rest/fbandroid"
+        "fbobjc" = ".ovrsource-rest/fbobjc"
+        "xplat" = ".ovrsource-rest/xplat"
diff --git a/tests/integration/library.sh b/tests/integration/library.sh
index 213164a935..a46988afa4 100644
--- a/tests/integration/library.sh
+++ b/tests/integration/library.sh
@@ -369,6 +369,10 @@ db.local_db_path = "$TESTTMP/disabled_repo"
 CONFIG
 }
 
+function setup_commitsyncmap {
+  cp "$TEST_FIXTURES/commitsyncmap.toml" "$TESTTMP/mononoke-config/common/commitsyncmap.toml"
+}
+
 function setup_mononoke_repo_config {
   cd "$TESTTMP/mononoke-config" || exit
   local reponame="$1"
diff --git a/tests/integration/test-megarepo-tool.t b/tests/integration/test-megarepo-tool.t
index 8a3073007b..8cd7ac56d3 100644
--- a/tests/integration/test-megarepo-tool.t
+++ b/tests/integration/test-megarepo-tool.t
@@ -4,6 +4,7 @@ setup configuration
 
   $ REPOTYPE="blob:files"
   $ setup_common_config $REPOTYPE
+  $ setup_commitsyncmap
 
   $ cd $TESTTMP
 
@@ -23,7 +24,7 @@ setup hg server repo
   $ hg ci -m "fbsource-like commit"
   $ hg book -r . fbsourcemaster
 
--- create soem semblance of ovrsource
+-- create some semblance of ovrsource
   $ hg up null -q
   $ createfile fbcode/fbcodfile_ovrsource
   $ createfile fbobjc/fbobjcfile_ovrsource
@@ -50,23 +51,23 @@ blobimport
 
   $ export COMMIT_DATE="1985-04-12T23:20:50.52Z"
 move things in fbsource
-  $ megarepo_tool move fbsource 4da689e6447cf99bbc121eaa7b05ea1504cf2f7c user "fbsource move" --mark-public --commit-date-rfc3339 "$COMMIT_DATE"
+  $ megarepo_tool move 1 4da689e6447cf99bbc121eaa7b05ea1504cf2f7c user "fbsource move" --mark-public --commit-date-rfc3339 "$COMMIT_DATE"
   * using repo "repo" repoid RepositoryId(0) (glob)
   * Requesting the hg changeset (glob)
-  * Hg changeset: HgChangesetId(HgNodeHash(Sha1(ed8feccfa30ef541a15a1616e4e4db66ee7f91e2))) (glob)
+  * Hg changeset: HgChangesetId(HgNodeHash(Sha1(2d1c2ac8acbc245768933d05d23bd248cf6a16bb))) (glob)
   * Marking changeset as public (glob)
   * Done marking as public (glob)
 
 move things in ovrsource
-  $ megarepo_tool move ovrsource 4d79e7d65a781c6c80b3ee4faf63452e8beafa97 user "ovrsource move" --mark-public --commit-date-rfc3339 "$COMMIT_DATE"
+  $ megarepo_tool move 2 4d79e7d65a781c6c80b3ee4faf63452e8beafa97 user "ovrsource move" --mark-public --commit-date-rfc3339 "$COMMIT_DATE"
   * using repo "repo" repoid RepositoryId(0) (glob)
   * Requesting the hg changeset (glob)
-  * Hg changeset: HgChangesetId(HgNodeHash(Sha1(88783bf39cdb412fbc8762d45bad226470b381c6))) (glob)
+  * Hg changeset: HgChangesetId(HgNodeHash(Sha1(3c5f72c6d1ed24bd0914ff5ecd96b98f216002b4))) (glob)
   * Marking changeset as public (glob)
   * Done marking as public (glob)
 
 merge things in both repos
-  $ megarepo_tool merge ed8feccfa30ef541a15a1616e4e4db66ee7f91e2 88783bf39cdb412fbc8762d45bad226470b381c6 user "megarepo merge" --mark-public --commit-date-rfc3339 "$COMMIT_DATE"
+  $ megarepo_tool merge 2d1c2ac8acbc245768933d05d23bd248cf6a16bb 3c5f72c6d1ed24bd0914ff5ecd96b98f216002b4 user "megarepo merge" --mark-public --commit-date-rfc3339 "$COMMIT_DATE"
   * using repo "repo" repoid RepositoryId(0) (glob)
   * Creating a merge commit (glob)
   * Checking if there are any path conflicts (glob)
@@ -74,8 +75,8 @@ merge things in both repos
   * Creating a merge bonsai changeset with parents: * (glob)
   * Marked as public * (glob)
   * Created *. Generating an HG equivalent (glob)
-  * Hg changeset: HgChangesetId(HgNodeHash(Sha1(fa2c1aadd78fd99ca6e45a0e1d8b5a80182cf908))) (glob)
-  $ mononoke_admin bookmarks set master fa2c1aadd78fd99ca6e45a0e1d8b5a80182cf908
+  * Hg changeset: HgChangesetId(HgNodeHash(Sha1(0383059155f1a61cdba994a8bb686c15f378794b))) (glob)
+  $ mononoke_admin bookmarks set master 0383059155f1a61cdba994a8bb686c15f378794b
   * using repo "repo" repoid RepositoryId(0) (glob)
 
 start mononoke server