Compare Current Branch Against Upstream Default

Compare the current branch against the upstream default branch and view the full diff.

Step 1: Determine BASE_REF

Run:

git remote -v

If upstream remote exists, run:

DEFAULT_BRANCH=$(gh repo view $(git remote get-url upstream) --json defaultBranchRef --jq '.defaultBranchRef.name') && echo "upstream/$DEFAULT_BRANCH"

Otherwise, run:

DEFAULT_BRANCH=$(gh repo view --json defaultBranchRef --jq '.defaultBranchRef.name') && echo "origin/$DEFAULT_BRANCH"

Set BASE_REF to the output (e.g., upstream/main).

Step 2: Fetch and View Commits

git fetch ${BASE_REF%%/*} && git log --oneline $BASE_REF...HEAD

Step 3: View Diff Stats

Run --stat first to get an overview of changes per file:

git diff $BASE_REF...HEAD --stat

This shows files changed and lines added/removed. Use this to:

• Identify noisy files to exclude (lock files, generated code with 1000s of lines)
• Determine if pagination is needed (large total line count)
• Get a quick overview before diving into the full diff

Step 4: View Full Diff

git diff $BASE_REF...HEAD -U20

always exclude noisy files, use pathspec excludes. Add patterns as needed based on the project:

git diff $BASE_REF...HEAD -U20 -- \
  ':!*.lock' \
  ':!package-lock.json' \
  ':!pnpm-lock.yaml'

Common files to exclude

Lock files:

• *.lock, package-lock.json, pnpm-lock.yaml, yarn.lock, bun.lockb

Generated code (committed but auto-generated):

• */generated/*, *.generated.ts, *.gen.ts, *.gen.go
• OpenAPI/Swagger generated clients
• Protobuf generated files: *.pb.go, *_pb.ts

Snapshots (if reviewing logic, not snapshot updates):

• *.snap, __snapshots__/*

only do this if you already know about files to exclude from your existing context

Paginating Large Diffs

For large diffs, paginate using sed to view specific line ranges with no overlap:

# Page 1: lines 1-500
git diff $BASE_REF...HEAD -U20 -- ':!*.lock' | sed -n '1,500p'

# Page 2: lines 501-1000
git diff $BASE_REF...HEAD -U20 -- ':!*.lock' | sed -n '501,1000p'

# Page 3: lines 1001-1500
git diff $BASE_REF...HEAD -U20 -- ':!*.lock' | sed -n '1001,1500p'

Continue incrementing by 500 until output is empty.