Patch collaboration quick reference

# Generate patches from the last 3 commits
git format-patch -3 -o /tmp/patches/

# Generate a single commit as a patch
git format-patch -1 <sha> --stdout > change.patch

# Include a cover letter for a series
git format-patch main..feature --cover-letter -o /tmp/patches/

# Apply a series with three-way fallback
git am --3way /tmp/patches/*.patch

# Apply a single patch without committing
git am --no-commit change.patch

# Resolve a conflict and continue (no editor prompt)
git add . && git am --resolved

# Skip a failing patch and continue the series
git am --skip

# Abort the entire am session
git am --abort

# Dry-run before applying a raw diff
git apply --check --3way change.diff

# Apply a raw diff to working tree only
git apply change.diff

# Apply a raw diff to index and working tree
git apply --index change.diff

# Reverse a previously applied patch
git apply -R change.diff

# Show what a patch claims to change
git apply --stat change.diff

# Verify round-trip losslessness
git format-patch -1 HEAD --stdout > verify.patch
git reset --hard HEAD~1
git am verify.patch
git diff HEAD^ HEAD --stat

Key flags

Flag	When to use
--3way	Patch context drifted from the target tree. Always use in CI.
--signoff	Append Signed-off-by to certify authorship.
--binary	Patch range may include binary files.
--stdout	Emit single stream for pipe or artifact storage.
--base=<sha>	Record the merge base so the consumer can find common ancestors.
--resolved	Continue after conflict without editor prompt.
--no-commit	Inspect the patch effect before committing.
--check	Test that a diff applies without touching the tree.

DevOps patterns

# CI gate: does the patch apply cleanly?
if ! git apply --check --3way /artifacts/change.diff; then
  echo "patch does not apply to this tree"
  exit 1
fi

# CI apply with authorship preserved
git am --3way --signoff /artifacts/patches/*.patch

# Backport from main to release branch
cd /repos/target
git checkout release/v2.3
git am --3way /tmp/backport/0001-*.patch

# Rebase a patch series locally
git am /tmp/patches/*.patch
git rebase -i <base>
git format-patch <base> -o /tmp/patches-v2/