Hi@akhtar,
The following merge-branches-by-fast-forward example merges the specified source branch with the specified destination branch in a repository named MyDemoRepo.
$ aws codecommit merge-branches-by-fast-forward \
    --source-commit-specifier bugfix-bug1234 \
    --destination-commit-specifier bugfix-bug1233 \
    --repository-name MyDemoRepo