git.txt

Nice — here’s the commit graph diagram you asked for. This shows how your history looks depending on whether you merge or rebase.

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A) Merge workflow (preserves full branch graph)

Upstream main:   A──B──C───────────────┐
                                        │
Your branch:     A──B──C──D──E─────────┴─M
                                             ↑
                                             Merge commit (M)

	•	You branched from commit C.
	•	You added commits D and E.
	•	Upstream added commits after C.
	•	When you git merge upstream/main, Git creates a merge commit (M) joining both histories.
	•	History shows branching + merging — good for context but can look messy.

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B) Rebase workflow (linear history, no merge commit)

Upstream main:   A──B──C──F──G──H
                               │
Your branch after rebase:       D'──E'

	•	Same start at commit C.
	•	Upstream added commits F, G, H.
	•	When you git rebase upstream/main, your commits (D, E) are replayed on top of the new tip H, becoming D' and E'.
	•	Result: looks like you developed your feature after the latest upstream work — clean linear history.
	•	Requires --force-with-lease when pushing, because commit hashes change.

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C) Side-by-side: Merge vs Rebase

Merge history (graphy):

A──B──C───────────────F──G──H
       └──D──E──────────────┘

Rebase history (linear):

A──B──C──F──G──H──D'──E'


⸻

D) When to use what
	•	Merge →
	•	If you want to preserve the “real” history (showing when branches diverged).
	•	Safer for beginners (no rewriting commits).
	•	Good for long-lived feature branches.
	•	Rebase →
	•	If you want a clean, straight line history.
	•	Preferred in open-source PR workflows.
	•	Requires confidence resolving conflicts & force-pushing.

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E) Common commands

Merge workflow:

git checkout feature-branch
git fetch upstream
git merge upstream/main
git push origin feature-branch

Rebase workflow:

git checkout feature-branch
git fetch upstream
git rebase upstream/main
# fix conflicts if needed
git push origin feature-branch --force-with-lease


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So: Merge = “historical diary” (records exactly what happened).
Rebase = “rewrite the story” (makes it look like you developed cleanly on top).

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