Gpd Compare Branches

<required_reading> Read all files referenced by the invoking prompt's execution_context before starting. </required_reading>

git branch --list 'hypothesis/*' --format='%(refname:short)'

If no hypothesis branches found:

ERROR: No hypothesis branches found.

Create hypothesis branches with $gpd-branch-hypothesis <description>

Exit.

If exactly 1 hypothesis branch found:

Single-branch mode: compare the one hypothesis branch against its parent branch as baseline. This allows evaluating a hypothesis without requiring a second alternative. Proceed to extract_branch_data with the hypothesis branch and its parent.

Record the current branch:

CURRENT_BRANCH=$(git rev-parse --abbrev-ref HEAD)

git show {branch}:.gpd/STATE.md 2>/dev/null
git show {branch}:.gpd/hypotheses/{slug}/HYPOTHESIS.md 2>/dev/null

If STATE.md is missing on a branch: Mark the branch as "no state data" in the comparison table. This branch has no completed work to compare.

If HYPOTHESIS.md is missing: The branch was created manually without $gpd-branch-hypothesis. Use the branch name as the description and mark hypothesis metadata as "N/A".

For each branch, collect:

1. Hypothesis description -- from HYPOTHESIS.md ## Description
2. Status -- from HYPOTHESIS.md ## Metadata -> Status field
3. Current phase -- from STATE.md ## Current Position
4. Key results -- scan for SUMMARY.md files in the branch:

git ls-tree -r --name-only {branch} -- .gpd/phases/ | grep SUMMARY.md

For each SUMMARY.md found:

git show {branch}:{summary_path} 2>/dev/null

Extract via summary-extract --field one_liner --field key_results --field equations: one_liner (body bold text or frontmatter), key_results (body section), equations (body section "Equations Derived").

5. Verification status -- scan for VERIFICATION.md files:

git ls-tree -r --name-only {branch} -- .gpd/phases/ | grep VERIFICATION.md

Extract status (passed/gaps_found/human_needed) from each.

6. Commit count -- number of commits unique to this branch:

git rev-list --count {branch} --not $(git merge-base {branch} {parent_branch})

Determine parent from the first hypothesis branch's HYPOTHESIS.md ## Metadata -> Parent branch field. If HYPOTHESIS.md is missing on that branch, fall back to main.

Extract the same data (STATE.md, SUMMARYs, VERIFICATIONs) from the parent branch so it can be included in the comparison as the baseline.

If no branch has any SUMMARY.md files:

No completed plans found on any branch. Nothing to compare yet.

Complete at least one plan on each branch before comparing:
  $gpd-execute-phase <phase-number>

Exit. </step>

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 GPD > BRANCH COMPARISON
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## Overview

| Branch | Description | Phase | Plans Done | Verified |
|--------|-------------|-------|------------|----------|
| {parent} (baseline) | Original approach | {N} | {X}/{Y} | {status} |
| hypothesis/{slug-1} | {description} | {N} | {X}/{Y} | {status} |
| hypothesis/{slug-2} | {description} | {N} | {X}/{Y} | {status} |

## Key Results Comparison

### {Result Category} (e.g., "Energy Spectrum", "Transport Coefficients")

| Quantity | {parent} | hypothesis/{slug-1} | hypothesis/{slug-2} |
|----------|----------|---------------------|---------------------|
| {quantity-1} | {value} | {value} | {value} |
| {quantity-2} | {value} | {value} | {value} |

### Equations

| Branch | Key Equations |
|--------|---------------|
| {parent} | {eq list} |
| hypothesis/{slug-1} | {eq list} |
| hypothesis/{slug-2} | {eq list} |

## Verification Summary

| Branch | Checks Passed | Warnings | Failures | Overall |
|--------|---------------|----------|----------|---------|
| {parent} | {N} | {N} | {N} | {status symbol} |
| hypothesis/{slug-1} | {N} | {N} | {N} | {status symbol} |
| hypothesis/{slug-2} | {N} | {N} | {N} | {status symbol} |

When branches produce numerical results (extracted from key_results in SUMMARY.md frontmatter), compute quantitative differences:

1. Extract numerical values from each branch:

For each branch, scan all SUMMARY.md key_results entries for values with numbers (e.g., E_0 = -1.234 +/- 0.005, T_c/J = 2.269):

Prefer parsing the git show output directly in memory. The branch SUMMARY content is already available from git show, so do not write it to .gpd/tmp/ just to run a path-based extractor.

If the structure is ambiguous, re-run git show {branch}:{summary_path} 2>/dev/null and inspect the frontmatter plus the ## Key Results and ## Equations Derived sections directly. Keep branch-summary extraction in memory/stdout only; do not use .gpd/tmp/, /tmp, or another temp root for this step.

Parse each entry for: quantity name, numerical value, uncertainty (if present), units.

2. Match quantities across branches:

Identify quantities that appear in two or more branches (by matching quantity names or equation labels). Build a matched-pairs table.

3. Compute relative differences:

For each matched quantity pair between branches A and B:

relative_diff = |value_A - value_B| / max(|value_A|, |value_B|)

If both values have uncertainties (sigma_A, sigma_B):

combined_sigma = sqrt(sigma_A^2 + sigma_B^2)
tension = |value_A - value_B| / combined_sigma

4. Flag statistically significant disagreements:

For values without uncertainties, use relative difference thresholds:

• < 1%: consistent
• 1-5%: mild difference (!)
• 5-10%: notable difference (!!)

• 10%: large difference (!!!)

5. Present numerical comparison table:

## Numerical Comparison

| Quantity | {parent} | hypothesis/{slug} | Rel. Diff | Tension | Flag |
|----------|----------|-------------------|-----------|---------|------|
| E_0      | -1.234(5) | -1.237(4) | 0.24% | 0.47σ | — |
| T_c/J    | 2.269(3) | 2.315(8) | 2.0% | 5.4σ | !!! |

{If any flags:}
### Significant Disagreements

**T_c/J:** 5.4σ tension between branches. The hypothesis branch predicts a higher
critical temperature. This {agrees with / contradicts} the hypothesis expectation
that {reference HYPOTHESIS.md expected outcome}.

6. If no numerical results found in any branch: Skip this step silently (branches may contain purely analytical results).

## Assessment

{For each branch: 2-3 sentences on strengths/weaknesses relative to others.
Consider: accuracy, approximation validity, computational cost, generalizability, verification completeness.
If numerical comparison was performed, reference significant agreements and disagreements.}

**Recommendation:** {Which branch appears most promising, with reasoning.
If inconclusive, say so and suggest what additional work would distinguish them.}

───────────────────────────────────────────────────────────────

## Actions

1. **Merge a branch** -- merge hypothesis results back to parent
2. **Delete a branch** -- clean up an abandoned hypothesis
3. **Continue working** -- return to current branch
4. **Export comparison** -- write this comparison to .gpd/BRANCH-COMPARISON.md

Which action? (1/2/3/4)

───────────────────────────────────────────────────────────────

If merge selected:

1. Ask which branch to merge
2. Confirm the merge target (parent branch)
3. Switch to parent branch:

git checkout {parent_branch}

4. Merge the hypothesis branch:

git merge hypothesis/{slug} --no-ff -m "merge: incorporate hypothesis/{slug} results"

5. If merge conflicts:

╔══════════════════════════════════════════════════════════════╗
║  CHECKPOINT: Decision Required                               ║
╚══════════════════════════════════════════════════════════════╝

Merge conflicts detected in:
{list of conflicted files}

──────────────────────────────────────────────────────────────
→ Resolve conflicts manually, then type "done"
──────────────────────────────────────────────────────────────

6. After successful merge, offer to delete the merged branch:

git branch -d hypothesis/{slug}

If delete selected:

1. Ask which branch to delete
2. Confirm deletion (warn about data loss if unmerged)
3. Execute: git branch -D hypothesis/{slug} (if confirmed)

If export selected:

Write the comparison output to .gpd/BRANCH-COMPARISON.md.

PRE_CHECK=$(/Users/charlie/.gpd/venv/bin/python -m gpd.runtime_cli --runtime codex --config-dir ./.codex --install-scope local pre-commit-check --files .gpd/BRANCH-COMPARISON.md 2>&1) || true
echo "$PRE_CHECK"

/Users/charlie/.gpd/venv/bin/python -m gpd.runtime_cli --runtime codex --config-dir ./.codex --install-scope local commit "docs: export branch comparison" --files .gpd/BRANCH-COMPARISON.md

git checkout {CURRENT_BRANCH}

Present completion:

───────────────────────────────────────────────────────────────

**Also available:**
- `$gpd-branch-hypothesis <desc>` -- create another hypothesis branch
- `$gpd-progress` -- check overall research progress
- List branches: `git branch --list 'hypothesis/*'`

───────────────────────────────────────────────────────────────

<anti_patterns>

• Don't compare branches with no completed plans -- there's nothing to compare
• Don't auto-merge without user confirmation
• Don't delete branches without checking if they have unmerged results
• Don't leave the user on a different branch than where they started
• Don't force-push or rebase hypothesis branches
• Don't compare only commit counts -- focus on physics results and verification status </anti_patterns>

<success_criteria> Branch comparison is complete when:

• All hypothesis branches discovered and listed
• Parent branch identified and included as baseline
• STATE.md and SUMMARY data extracted from each branch
• Verification status collected from each branch
• Structured comparison table presented
• Numerical comparison computed for shared quantities (if both branches have numerical results)
• Statistically significant disagreements flagged with tension values
• Assessment with recommendation provided
• Action offered (merge/delete/continue/export)
• User returned to original branch

</success_criteria>

</execution_context>