Besides Git merge being a common operation when merging one branch into another, there are these two popular flags bamboozling developers: --ff or so-called fast-forward, and --no-ff meaning no fast-forward. It comes down to whether to create a merge commit or not.
Prerequisites
- Git
Solution
--ff
By default, merging is done including the --ff parameter. What it means is, it does not create a merge commit, instead updates the branch pointer (HEAD) to point to the tip of the merged branch (the latest commit).
A common example would be when running the git pull command in order to update the branch (pull changes). Under the hood git pull = git fetch + git merge.
git checkout develop
git pull develop
or, the equivalent:
git checkout develop
git fetch --prune && git merge develop --ff
Note: Excluding the --ff leads to the same behavior as it’s the default one.
However, that’s not always the case. The merge command will try to create a merge commit only when the merged branch is not a descendant of the current Git history meaning the merged branch commit(s) are not children, or great-children, or great-great-children, etc. of the current commit. This is where --no-ff comes into play.
--no-ff
Forces to always create a merge commit. For instance merging a feature or develop branch into main, or even merging a GitHub pull request would be the same thing.
Example merging feature-abc branch into develop.
git checkout develop
git fetch --prune && git pull develop
git merge feature-abc --no-ff
--ff-only
Lastly, --ff-only will force not to create a merge commit although when it’s not possible, the merge will be cancelled and exits with a non-zero code.
Conclusion
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