Create an article about `Merge Methods`

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Merge Methods

Merge methods refer to the specific procedures or commands used to perform the integration of changes in Git. They determine the actual merge process and the resulting structure of the commit history.

• 1. Category
  • 1.1. Implicit Merging
  • 1.1.1. Fast-Forward Merge
  • 1.1.2. Squash Merge
  • 1.1.3. Rebase Merge
  • 1.2. Explicit Merging
  • 1.2.1. Merge Commit
  • 1.2.2. Semi-Linear Merge
• 2. Terminology
• 3. References

1. Category

1.1. Implicit Merging

Implicit merging involves incorporating changes from one branch into another in a straightforward, sequential manner with a linear history.

1.1.1. Fast-Forward Merge

Moves the branch pointer forward without creating a new commit if possible.

1. Commands and Operations

   git checkout main
   git merge --ff feature

2. Representations and Diagrams

   • Before Merge

     gitGraph
       commit id: "A"
       branch feature
       checkout feature
       commit id: "B"
       checkout main
       commit id: "C"
       checkout feature
       commit id: "D"
       checkout main
       commit id: "E"
       checkout feature
       commit id: "F"

   • After Merge

     gitGraph
       commit id: "A"
       commit id: "B"
       commit id: "C"
       commit id: "D"
       commit id: "E"
       commit id: "F"

1.1.2. Squash Merge

Combines all changes from a feature branch into a single commit before merging, maintaining a cleaner commit history.

1. Commands and Operations

   git checkout feature
   git merge --squash feature
   git commit -m "feat: create API rate limits using RPM (requests per minute)"
   git checkout main
   git merge --ff feature

2. Representations and Diagrams

   • Before Merge

     gitGraph
       commit id: "A" type: HIGHLIGHT
       branch feature
       checkout feature
       commit id: "B"
       checkout main
       commit id: "C" type: HIGHLIGHT
       checkout feature
       commit id: "D"
       checkout main
       commit id: "E" type: HIGHLIGHT
       checkout feature
       commit id: "F"

   • After Merge

     gitGraph
       commit id: "A" type: HIGHLIGHT
       commit id: "C" type: HIGHLIGHT
       commit id: "E" type: HIGHLIGHT
       commit id: "G" type: HIGHLIGHT

1.1.3. Rebase Merge

Incorporates changes by rewriting the commit history of the feature branch and then fast-forward merging into the target branch.

1. Commands and Operations

   git checkout feature
   git rebase main
   git checkout main
   git merge --ff-only feature

2. Representations and Diagrams

   • Before Merge

     gitGraph
       commit id: "A"
       branch feature
       checkout feature
       commit id: "B"
       checkout main
       commit id: "C"
       checkout feature
       commit id: "D"
       checkout main
       commit id: "E"
       checkout feature
       commit id: "F"

   • After Merge

     gitGraph
       commit id: "A"
       commit id: "C"
       commit id: "E"
       commit id: "B"
       commit id: "D"
       commit id: "F"

1.2. Explicit Merging

Explicit merging involves integrating changes from multiple branches in a more complex manner, often creating non-linear history branch structures.

1.2.1. Merge Commit

1. Commands and Operations

   git checkout main
   git commit -m "chore: merge `feature` into `main`"
   git merge --no-ff feature

2. Representations and Diagrams

   • Before Merge

     gitGraph
       commit id: "A"
       branch feature
       checkout feature
       commit id: "B"
       checkout main
       commit id: "C"
       checkout feature
       commit id: "D"
       checkout main
       commit id: "E"
       checkout feature
       commit id: "F"

   • After Merge

     gitGraph
       commit id: "A"
       branch feature
       checkout feature
       commit id: "B"
       checkout main
       commit id: "C"
       checkout feature
       commit id: "D"
       checkout main
       commit id: "E"
       checkout feature
       commit id: "F"
       checkout main
       merge feature id: "G"
       checkout main

1.2.2. Semi-Linear Merge

A semi-linear merge in Git is a mix of a rebase and a merge.

1. Commands and Operations

   git checkout feature
   git rebase main
   git checkout main
   git merge --no-ff feature

2. Representations and Diagrams

   • Before Merge

     gitGraph
       commit id: "A"
       branch feature
       checkout feature
       commit id: "B"
       checkout main
       commit id: "C"
       checkout feature
       commit id: "D"
       checkout main
       commit id: "E"
       checkout feature
       commit id: "F"

   • After Merge

     gitGraph
       commit id: "A"
       commit id: "C"
       commit id: "E"
       branch feature
       checkout feature
       commit id: "B"
       commit id: "D"
       commit id: "F"
       checkout main
       merge feature id: "G"
       checkout main

2. Terminology

Understanding these terms can help developers navigate and communicate effectively when working with Git merging strategies.

• Fast-Forward Merge

  A merge strategy where the branch pointer is moved forward without creating a new commit if possible.

• Recursive Merge

  A merge strategy that creates a new commit to integrate changes from one branch into another, allowing non-linear development.

• Three-Way Merge

  A merge strategy that incorporates changes from two branches and their common ancestor to create a new commit, resolving conflicts when necessary.

• Octopus Merge

  A merge strategy that merges multiple branches simultaneously, creating a merge commit with more than two parents.

• Subtree Merge

  A merge strategy that merges specific subtrees from one branch into another, useful for selective integration.

• Squash Merge

  A merge strategy that combines all changes from a feature branch into a single commit before merging, maintaining a cleaner commit history.

• Rebase and Merge

  A merge strategy that incorporates changes by rewriting the commit history of the feature branch and then fast-forward merging into the target branch.

• Implicit Merge

  Merging that happens automatically without direct user intervention, often during operations like pulls or fast-forward merges.

• Explicit Merge

  Merging initiated by a user using specific Git commands, such as git merge or git pull.

• Conflict Resolution

  The process of resolving conflicts that arise during a merge when changes in different branches cannot be automatically reconciled.

• Merge Commit

  A commit created during a merge operation that combines changes from multiple branches.

• Branch Divergence

  The situation where two branches have developed different sets of changes independently, leading to the need for merging.

• Rebase and Merge

  A merge method that incorporates changes by rewriting the commit history of the feature branch and then fast-forward merging into the target branch.

• Fast-Forward Merge

  A merge method that moves the branch pointer forward without creating a new commit if possible.

• No-Fast-Forward Merge

  A merge method that creates a new commit even when a fast-forward merge is possible, preserving a linear commit history.

• Squash and Merge

  A merge method that combines all changes from a feature branch into a single commit before merging for a cleaner commit history.

• Merge Commit

  A commit created during a merge operation that combines changes from multiple branches.

Understanding these terms provides a comprehensive overview of merging strategies and merge methods in Git.

3. References

• Git merge strategies page.
• Atlassian merge strategy page.
• W3docs merge strategies page.
• Microsoft pull requests with rebase page.

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