Merging combines changes from one branch into another — typically bringing a completed feature branch back into the main branch. Git handles most merges automatically, but understanding merge types and conflicts is important.
git switch main # be on the branch you want to merge INTO
git merge feature-x # merge feature-x's changes into main
You switch to the branch (the one receiving changes) and merge the branch into it.
FAST-FORWARD merge → if main hasn't changed since the branch was created, Git just
MOVES main's pointer forward to the branch's latest commit (no merge commit, linear)
MERGE COMMIT (three-way merge) → if BOTH branches have new commits, Git creates a new
"merge commit" combining them (has two parents) → preserves that a merge happened
→ git merge --no-ff forces a merge commit even when fast-forward is possible
Git fast-forwards when possible (simply advancing the pointer) or creates a merge commit (with two parents) when both branches diverged.
A CONFLICT happens when both branches changed the SAME lines differently — Git can't
auto-decide which to keep, so it asks YOU to resolve:
<<<<<<< HEAD
the version from the current branch (main)
=======
the version from the branch being merged (feature-x)
>>>>>>> feature-x
# resolve: edit the file to the desired result, remove the markers, then:
git add <file> # mark the conflict resolved
git commit # complete the merge
# git merge --abort # or cancel the merge entirely
Conflicts occur when both branches change the same lines — Git marks them and you manually choose the correct result, then stage and commit.
Understanding merging is essential because combining branch changes is a fundamental, constant part of collaborative Git workflows, so knowing how it works (including conflicts) is necessary everyday knowledge. Merging is how completed work (typically feature branches) gets integrated back into the main branch — the routine act of bringing changes together that happens continuously in team development.
Understanding the difference between a fast-forward merge (Git simply advancing the pointer when the target hasn't diverged, keeping history linear) and a merge commit (a three-way merge creating a new commit with two parents when both branches have new commits, recording that a merge happened) clarifies how Git integrates changes and what the resulting history looks like.
Most importantly, understanding merge conflicts — which occur when both branches change the same lines differently, so Git can't automatically decide and asks you to resolve — is crucial practical knowledge: conflicts are a normal, inevitable part of collaboration, and knowing how to recognize the conflict markers (<<<<<<<, =======, >>>>>>>), edit the file to the correct result, and complete the merge (stage and commit) is an essential skill that's often a source of anxiety for those who don't understand it.
Since integrating branch changes via merging is fundamental and constant in collaborative development, and since understanding merge types and especially resolving conflicts is necessary to combine work correctly (a routine, unavoidable task), understanding how merging works — basic merges, fast-forward vs merge commits, and conflict resolution — is essential, frequently-applied Git knowledge, a core skill for collaboration where conflict resolution in particular is a practical necessity every developer must handle confidently.