Fast-forward vs No-fast-forward

About

When merging branches in Git, the term fast-forward or no-fast-forward (--no-ff) describes how Git integrates the changes from one branch into another.

They do not affect the code content, but how Git writes commit history during the merge.

What Is a Fast-Forward Merge ?

A fast-forward merge happens when the branch being merged in is directly ahead of the current branch, with no divergent history. Git doesn’t need to create a new commit — it simply moves the pointer forward.

Visual Before Merge

main:  A -- B -- C
                   \
                 (feature): D -- E

If main is at C and you merge feature, and no new commits exist on main, Git will just move main forward.

After Fast-Forward Merge

main:  A -- B -- C -- D -- E

No merge commit is created.

Command

git checkout main
git merge feature

If main hasn't diverged, Git does a fast-forward by default.

What Is a No-Fast-Forward Merge ?

A no-fast-forward merge forces Git to always create a merge commit, even if a fast-forward is possible.

This makes the merge operation explicit in the history, preserving the fact that a merge occurred and from which branch.

Visual Before

main:       A -- B -- C
                       \
                      (feature): D -- E

After no-ff merge

main:        A -- B -- C ------ M
                        \       /
                         D -- E

Now there is a merge commit M, showing the integration point.

Command:

git checkout main
git merge --no-ff feature

Settings to Enforce Behavior

Always do no-fast-forward merges:

git config --global merge.ff false

This is useful in organizations that want explicit merge tracking.