Git Merging

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

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Git Merge

Different types of merges

Fast Forward Merge

• A 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.
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• How it works
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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.
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• How it works
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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:
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• git checkout main; git merge test
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Example: Three way merge

• Initial state:
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• Merge bugFix into main
  • Notice we are on the main branch
  • This essentially means make bugFix parent of main
  • git merge bugFix
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  • 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
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Tips

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
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• 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.

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Last updated: 2022-06-18