kandev/docs/plans/merge-commit-details/task-01-first-parent-merge-diff.md

id, title, status, wave, depends_on, plan, spec

id	title	status	wave	depends_on	plan	spec
01-first-parent-merge-diff	First-parent merge commit diff	done	1		plan.md	../../specs/merge-commit-details/spec.md

Task 01: First-parent merge commit diff

• Acceptance: GitOperator.ShowCommit returns the first-parent file map, patch, status, additions, and deletions for a clean two-parent merge; it does not include a feature-only file already present in the first parent; existing single-commit behavior and the CommitDiffResult contract remain unchanged.
• Verification: Follow strict TDD. Add the regression test and first run cd apps/backend && go test -v -run '^TestShowCommit_MergeCommitUsesFirstParentDiff$' ./internal/agentctl/server/process; confirm it fails because the merge result has no files. After the minimal fix, rerun that command, then run cd apps/backend && go test ./internal/agentctl/server/process and git diff --check from the repository root.
• Files likely touched: apps/backend/internal/agentctl/server/process/git_log.go, apps/backend/internal/agentctl/server/process/git_test.go, this task file, and plan.md for status/results synchronization.
• Dependencies: None.
• Parallelism: sequential — the test and implementation change the same Go package and must be completed as one Red-Green-Refactor cycle.
• Inputs: repair spec desired behavior and regression scenarios; GitOperator.ShowCommit and parseCommitDiff in git_log.go; existing setupTestRepo, runGit, TestParseCommitDiff_PathsWithSpaces, and TestShowCommit_NotCapped patterns.
• Output contract: Report the root-cause-preserving minimal change, exact files changed, RED and GREEN command results, process-package result, git diff --check, remaining risks, and synchronized task/plan statuses.

Results

• RED: rtk go test -v -run '^TestShowCommit_MergeCommitUsesFirstParentDiff$' ./internal/agentctl/server/process failed with the expected assertion: merge diff missing incoming first-parent change; files=[].
• GREEN: the same focused command passed with 1 test passed.
• Full package: rtk go test ./internal/agentctl/server/process passed with 550 tests in 1 package (exit code 0).
• Hygiene: git diff --check passed. gofmt ran on the two Go files. Test repositories were temporary and cleaned by t.Cleanup; no external state, browser session, or live instance was modified.