script/ceph-backport: skip fetch if merge commit already exists locally

If the merge commit is already present in the local object store, there
is no need to fetch it from the upstream remote. Use git-cat-file to
check before fetching, avoiding unnecessary network traffic.

Signed-off-by: Kefu Chai <tchaikov@gmail.com>

diff --git a/src/script/ceph-backport.sh b/src/script/ceph-backport.sh
index 4f90ff93cfa78ac9fcdf5c268dd33a3e2bf0a18a..85e861c9cda42fd71b0244325fc3be09d71ec2d1 100755 (executable)
--- a/src/script/ceph-backport.sh
+++ b/src/script/ceph-backport.sh
@@ -294,7 +294,9 @@ function cherry_pick_phase {
         git checkout -b "$local_branch" FETCH_HEAD
     fi
 
-    git fetch "$CEPH_UPSTREAM" "$merge_commit_sha"
+    if ! git cat-file -e "${merge_commit_sha}^{commit}" 2>/dev/null; then
+        git fetch "$CEPH_UPSTREAM" "$merge_commit_sha"
+    fi
 
     set +x
     maybe_restore_set_x