In brief
git merge incorporates changes from another history into the current branch. A linear relationship can allow a fast-forward; divergent history can produce a separate merge commit.
Useful to know
git merge incorporates changes from another history into the current branch. A linear relationship can allow a fast-forward; divergent history can produce a separate merge commit. [1]
Absence of textual conflicts does not prove the combined logic is correct. Changes can merge mechanically while breaking behaviour. After integration, run the relevant checks for the affected functionality.
Sources
For further detail and to check the information: