Agent Skills: Include BOTH the old line (47) AND new line (47)

Create incremental, atomic commits for the current changes. Think deeply about how to break down changes into logical, atomic commits that each tell part of the story.

Initial Analysis Phase

1. git status to see all modified/untracked files
2. git diff to analyze all unstaged changes
3. git diff --cached to see any already staged changes
4. hunk diff --json to get machine-readable output with exact line numbers
5. git log --oneline -10 to understand recent commit style
6. Check CLAUDE.md for project-specific guidelines

Commit Planning Phase

Analyze changes comprehensively and develop a mental model of the commit sequence.

Categorize changes into logical groups:

• Isolated bug fixes: Can be committed independently
• Refactoring: File moves, function reorganization, code cleanup
• New features: Core implementation separate from integration
• Test additions: Separate from implementation when possible
• Documentation updates: Usually their own commit

Special File Classification

Identify files that should be committed separately:

• Lock files: go.sum, package-lock.json, yarn.lock, Cargo.lock
• Generated files: *.pb.go, *_gen.go, *.generated.*
• Test files: Can often be separate from implementation

Staging Strategies

Whole Files

When entire files form a logical unit:

git add src/feature.go src/feature_test.go
git commit -m "feature: add new capability"

Line-Level with Hunk

When changes within a file need to be split:

hunk diff                     # See line numbers
hunk stage file.go:10-25      # Stage bug fix lines
hunk preview                  # Verify patch
hunk commit -m "fix: ..."
hunk stage file.go:40-60      # Stage feature lines
hunk commit -m "feat: ..."

Understanding Hunk Line Numbers

The hunk diff output shows two columns of line numbers:

• Left column (OLD): Line numbers in the original file (before changes)
• Right column (NEW): Line numbers in the modified file (after changes)

Line number semantics by operation type:

• Additions (lines with +): Use NEW file line numbers (right column)
• Deletions (lines with -): Use OLD file line numbers (left column)
• Replacements (delete + add): Include BOTH old and new line numbers

Staging Replacements

When staging changes that replace existing code (deletions followed by additions), you must include line numbers for both the deleted and added lines.

Example: Replacing a field assignment in a struct initialization:

   45     45   func NewService(cfg Config) *Service {
   46     46       return &Service{
-  47            backend:  cfg.Backend,    // OLD line 47 being deleted
+       47       client:   cfg.Client,     // NEW line 47 being added
   48     48       timeout: cfg.Timeout,

To stage this replacement correctly:

# Include BOTH the old line (47) AND new line (47)
hunk stage service.go:47

# Verify the patch includes both deletion and addition
hunk preview

For more complex replacements spanning multiple lines:

   100    100   type Handler struct {
-  101          conn    net.Conn       // OLD lines 101-102 deleted
-  102          active  bool
+      101      client  *Client        // NEW lines 101-103 added
+      102      ready   bool
+      103      ctx     context.Context
   103    104   }

Stage with ranges covering both old and new:

# Old lines 101-102 (deletions) + new lines 101-103 (additions)
hunk stage handler.go:101-103

Verification Workflow

Always verify before committing:

hunk diff --json              # Get exact line numbers
hunk stage file.go:LINES      # Stage the change
hunk preview                  # Verify patch looks correct
# If wrong, reset and try again:
hunk reset

Multiple Files, Specific Lines

hunk stage api.go:15-30 handler.go:8-12
hunk commit -m "refactor: extract validation logic"

Pattern-Based

git add "*_test.go"           # All test files
git add "lnwallet/*.go"       # All files in a package

Dependency Detection

When function signatures change, find all callers:

# Using ast-grep for structural search
sg run -p '$FUNC($$$ARGS)' -l go

# Or grep for simpler cases
grep -r "funcName" --include="*.go" .

If changes are deeply intertwined, explain why they must be committed together.

Commit Message Format

DO NOT overuse bullet points. Messages should read as natural prose.

subsystem: Brief summary (imperative mood, <50 chars)

In this commit, we [explain the change in natural prose, focusing
on the "why" more than the "what"]. This change improves [aspect]
by [approach/method].

[Additional context about trade-offs, alternatives considered,
or implementation details if needed. Keep prose natural.]

[For bug fixes, explain the root cause and the fix approach.]

Subsystem Prefix Guidelines

• Single package: package: description
• Multiple packages: pkg1+pkg2: description or multi: description
• Project-wide: multi: description
• Build/CI: build: or ci:
• Documentation: docs:
• Tests: test: or package/test:

Execution Flow

1. Analyze all changes comprehensively
2. Create a mental model of the commit sequence
3. For each planned commit:
   • hunk stage FILE:LINES or git add for whole files
   • hunk preview to verify the patch looks correct
   • Craft a detailed commit message
   • hunk commit -m "message"
4. Continue until all changes are committed

Special Considerations

• For generated files, commit them separately with clear indication
• For vendored dependencies, use a dedicated commit
• Skip CI for trivial changes with [skip ci] suffix

Focus area: $ARGUMENTS