git merge incomingBranch

This merges the branch incomingBranch into the branch you are currently in. For example, if you are currently in master, then incomingBranch will be merged into master.

Merging can create conflicts in some cases. If this happens, you will see the message Automatic merge failed; fix conflicts and then commit the result. You will need to manually edit the conflicted files, or to undo your merge attempt, run:

git merge --abort

When the commits on two branches don't conflict, Git can automatically merge them:

~/Stack Overflow(branch:master) » git merge another_branch
Auto-merging file_a
Merge made by the 'recursive' strategy.
 file_a | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

After starting a merge, you might want to stop the merge and return everything to its pre-merge state. Use --abort:

git merge --abort

During a merge, you can pass --ours or --theirs to git checkout to take all changes for a file from one side or the other of a merge.

$ git checkout --ours   -- file1.txt # Use our version of file1, delete all their changes
$ git checkout --theirs -- file2.txt # Use their version of file2, delete all our changes

Default behaviour is when the merge resolves as a fast-forward, only update the branch pointer, without creating a merge commit. Use --no-ff to resolve.

git merge <branch_name> --no-ff -m "<commit message>"

Sometimes you might have branches lying around that have already had their changes merged into master. This finds all branches that are not master that have no unique commits as compared to master. This is very useful for finding branches that were not deleted after the PR was merged into master.

 for branch in $(git branch -r) ; do
   [ "${branch}" != "origin/master" ] && [ $(git diff master...${branch} | wc -l) -eq 0 ] && echo -e `git show --pretty=format:"%ci %cr" $branch | head -n 1`\\t$branch
 done | sort -r