git merge --no-ff-What is the difference between git merge and git merge --no-ff?

git merge no commit will merge the branches whereas git merge with --no-ff

Create a merge commit even when the merge resolves as a fast-forward. This is the default behavior when merging an annotated (and possibly signed) tag that is not stored in its natural place in refs/tags/hierarchy.

If you want to execute a git pull or use git merge to explicitly fast-forward, and you want to bail out (if it can't fast-forward), then you can use the --ff-only flag. This way you can regularly do something like git pull --ff-only