What is the difference between the merge and rebase commands?

The difference between merge and rebase lies in how they integrate changes from one branch into another.

Merge

• Preserves the commit history unchanged.
• Creates a new merge commit that combines changes.
• The history appears as intersecting branches.

// Example of history after merge
*--*--A--B (dev)
    \      \
     C--D---E (main) // E is the merge commit

• Well-suited for integrating changes when maintaining exact chronology is important.
• Can create a "noisy" history with many merge commits.

Rebase

• Rewrites the commit history.
• Takes commits from one branch and "reapplies" them on top of another branch.
• The history appears more linear.

// Example of history after rebase (rebasing dev onto main)
*--*--C--D--A'--B' (dev) // A' and B' are rewritten commits
    \
     E (main)       // Now main points to the same commit as before rebase

• Creates a cleaner and more linear history.
• Can lead to difficulties in collaborative work (if rebasing a branch that has already been published), as the history changes.
• May require resolving conflicts multiple times (once for each commit being reapplied, if conflicts occur).

Summary table:

Parameter	Merge	Rebase
Commit history	Preserved	Rewritten
New commits	One merge commit	No, existing commits are changed
Linearity of history	Less	More
Collaborative work	Safer (for published branches)	Can be risky (for published branches)
Conflicts	Resolved once	May be resolved multiple times