Skip to content

Git Merging

Links: - 106 Git Index
- Git - Branching, Rebasing & Merging

Git Merge

Different types of merges

Fast Forward Merge

  • fast-forward merge can occur when there is a linear path between branches that you want to merge.
  • If the master branch has not diverged, then we we try to merge master with hotfix instead of creating a new commit, it will just point master to the latest commit of the hotfix branch.
    • attachments/Pasted image 20220610195559.jpg
  • How it works
    • attachments/Pasted image 20220618160655.jpg

Three Way Merge

  • When there is not a linear path to the target branch, Git has no choice but to combine them via a three-way merge.
  • This merge uses an extra commit to tie together the two branches.
    • attachments/Pasted image 20220610195846.jpg
  • How it works
    • attachments/Pasted image 20220618160834.jpg
    • attachments/Pasted image 20220618160900.jpg

Merging Examples

Note the arrow direction in these examples.

They point backwards which is correct hence the notion of parent.

Example: 2 Way merge

  • Initial state:
    • attachments/Pasted image 20220609222826.jpg
  • git checkout main; git merge test
    • attachments/Pasted image 20220609222902.jpg

Example: Three way merge

  • Initial state:
    • attachments/Pasted image 20220609213233.jpg
  • Merge bugFix into main
    • Notice we are on the main branch
    • This essentially means make bugFix parent of main
    • git merge bugFix
    • attachments/Pasted image 20220609213327.jpg
    • If c3 was not there and main was at c1 then it would have directly moved to c2 if we did git merge bugFix from main : main says making bugFix parent not possible so get me there.
  • main now points to a commit that has two parents. If you follow the arrows up the commit tree from main, you will hit every commit along the way to the root.
  • This means that main contains all the work in the repository now.
  • Merging main to bugFix: making parent not possible get me there.
    • git checkout bugFix; git merge main
    • attachments/Pasted image 20220609214112.jpg


In merge the (current branch : branch-1) git merge branch-2. This means make branch-2 parent of branch-1.
  • Parent means behind
  • If making parent not possible then get me there.
  • git merge my-parent - for remembering
  • In short if you want to merge your feature branch changes to main then git checkout main; git merge feature
  • If you want to get all the changes made to main while you are working on your feature branch then git checkout feature; git merge main
    • We do this when we are working on something and we want the latest changes of main.

Merge Conflicts

  • Merge conflicts can occur while integrating commits from different sources
    • git merge, git rebase, git pull, git stash apply, git cherry-pick
  • We have merge conflicts when two commits have different information on the same line
    • attachments/Pasted image 20220618154953.jpg
  • Undo a conflict and start over:
    • git merge --abort
    • git rebase --abort
  • To resolve the merge conflict we just have to clean the file which will look something like this.
    >>>>>>>> branch name
    // changes
    // changes
    <<<<<<<< other branch
  • We can specify a merge tool to be used when we have merge conflicts in git.

Last updated: 2022-06-18