Merge branch 'conflict-resolution'

# Conflicts:
#	src/git.ts

CLAUDE.md

@@ -45,7 +45,7 @@ src/
     list.ts     # Show all active sessions with status
     save.ts     # Stage all changes and commit
     merge.ts    # Merge branch into main with conflict resolution
-    squash.ts   # Squash-merge branch into main (AI commit message) and close
+    squash.ts   # Squash all commits on a branch into a single commit (in-place)
     rebase.ts   # Rebase branch onto main with conflict resolution
     review.ts   # Launch grumpy code review with Claude
     diff.ts     # Show uncommitted changes or full branch diff
@@ -148,9 +148,9 @@ Always use `.nothrow()` for commands that may fail non-fatally. Use `.quiet()` t
 - `sandlot new` accepts a prompt instead of a branch name — derives a 2-word branch name via the Anthropic API (Haiku), falling back to simple text munging
 - `sandlot open` always passes `continue: true` to `vm.claude()` to resume the previous conversation
 - `sandlot save` uses `vm.claudePipe()` to generate commit messages from the staged diff
-- `sandlot merge`, `sandlot squash`, and `sandlot rebase` use `vm.claudePipe()` to resolve merge conflicts automatically
-- `sandlot squash` generates an AI commit message for the squash commit via `claudePipe()`; falls back to `"squash <branch>"`
-- `sandlot merge` and `sandlot squash` both delegate to `mergeAndClose()` in `helpers.ts`, which merges, resolves conflicts, commits, and then calls `closeAction()` to clean up
+- `sandlot merge` and `sandlot rebase` use `vm.claudePipe()` to resolve merge conflicts automatically
+- `sandlot squash` collapses all branch commits into a single commit in-place via `git reset --soft` to the merge base, then generates an AI commit message via `claudePipe()`; falls back to `"squash <branch>"`. Rolls back to the original HEAD on failure.
+- `sandlot merge` delegates to `mergeAndClose()` in `helpers.ts`, which merges, resolves conflicts, commits, and then calls `closeAction()` to clean up
 - `sandlot list` discovers missing session prompts by parsing Claude's `history.jsonl` from inside the container
 - `sandlot list` shows five status icons: idle (dim `◯`), active (cyan `◎`), dirty/unsaved (yellow `◐`), saved (green `●`), review (magenta `⦿`)
 - `sandlot review` sets `in_review` on the session during the review and clears it in a `finally` block on exit; `list` detects stale `in_review` flags (Claude not active) and clears them from state

src/cli.ts

@@ -141,9 +141,8 @@ program
 program
   .command("squash")
   .argument("<branch>", "branch name")
-  .option("-f, --force", "allow merging into a non-main branch")
-  .description("Squash-merge a branch into main and close the session")
-  .action((branch: string, opts: { force?: boolean }) => squashAction(branch, opts))
+  .description("Squash all commits on a branch into a single commit")
+  .action((branch: string) => squashAction(branch))
 
 program
   .command("rebase")

src/commands/helpers.ts

@@ -81,6 +81,29 @@ export async function teardownSession(root: string, branch: string, worktree: st
   await state.removeSession(root, branch)
 }
 
+/** Generated files to skip AI resolution — accept theirs and move on (basename match so `packages/foo/bun.lock` is also covered). */
+const SKIP_RESOLVE = new Set([
+  "bun.lock",
+  "bun.lockb",
+  "Cargo.lock",
+  "composer.lock",
+  "Gemfile.lock",
+  "go.sum",
+  "mix.lock",
+  "package-lock.json",
+  "Pipfile.lock",
+  "pnpm-lock.yaml",
+  "Podfile.lock",
+  "poetry.lock",
+  "pubspec.lock",
+  "flake.lock",
+  "gradle.lockfile",
+  "npm-shrinkwrap.json",
+  "Package.resolved",
+  "uv.lock",
+  "yarn.lock",
+])
+
 /** Resolve conflict markers in files using Claude, then stage them. */
 export async function resolveConflicts(
   files: string[],
@@ -90,15 +113,24 @@ export async function resolveConflicts(
   for (let i = 0; i < files.length; i++) {
     const file = files[i]
     onFile(file, i + 1, files.length)
-    const content = await Bun.file(join(cwd, file)).text()
+
+    if (SKIP_RESOLVE.has(basename(file))) {
+      await git.checkoutTheirs(file, cwd)
+      await git.stageFile(file, cwd)
+      continue
+    }
+
+    const content = await Bun.file(join(cwd, file)).text().catch(() => {
+      throw new Error(`Failed to read conflicted file: ${file}`)
+    })
 
     const resolved = await vm.claudePipe(
       content,
       "resolve this merge conflict. output ONLY the resolved file content with no markdown fences, no explanation, no surrounding text.",
     )
 
-    if (resolved.exitCode !== 0) {
-      throw new Error(`Claude failed to resolve ${file}: ${resolved.stderr}`)
+    if (resolved.exitCode !== 0 || !resolved.stdout.trim()) {
+      throw new Error(`Claude failed to resolve ${file}: ${resolved.stderr.trim() || "(no output)"}`)
     }
 
     await Bun.write(join(cwd, file), resolved.stdout.trimEnd() + "\n")
@@ -106,8 +138,8 @@ export async function resolveConflicts(
   }
 }
 
-/** Merge (or squash-merge) a branch into main, resolve conflicts if needed, and close the session. */
-export async function mergeAndClose(branch: string, opts?: { squash?: boolean; force?: boolean }): Promise<void> {
+/** Merge a branch into main, resolve conflicts if needed, and close the session. */
+export async function mergeAndClose(branch: string, opts?: { force?: boolean }): Promise<void> {
   const root = await git.repoRoot()
   const main = await git.mainBranch(root)
   const current = await git.currentBranch(root)
@@ -120,18 +152,11 @@ export async function mergeAndClose(branch: string, opts?: { squash?: boolean; f
     die(`Branch "${branch}" has unsaved changes. Run "sandlot save ${branch}" first.`)
   }
 
-  const label = opts?.squash ? "Squash-merged" : "Merged"
   const spin = spinner("Merging", branch)
-  const conflicts = await git.merge(branch, root, opts?.squash ? { squash: true } : undefined)
+  const conflicts = await git.merge(branch, root)
 
   if (conflicts.length === 0) {
-    if (opts?.squash) {
-      spin.text = "Starting container"
-      await vm.ensure((msg) => { spin.text = msg })
-      spin.text = "Generating commit message"
-      await squashCommit(branch, root)
-    }
-    spin.succeed(`${label} ${branch} into ${current}`)
+    spin.succeed(`Merged ${branch} into ${current}`)
     if (session) await teardownSession(root, branch, session.worktree)
     await git.deleteLocalBranch(branch, root).catch(() => {})
     return
@@ -147,15 +172,12 @@ export async function mergeAndClose(branch: string, opts?: { squash?: boolean; f
       spin.text = total > 1 ? `(${i}/${total}) Resolving ${file}` : `Resolving ${file}`
     })
 
-    if (opts?.squash) {
-      await squashCommit(branch, root)
-    } else {
-      await git.commitMerge(root)
-    }
-    spin.succeed(`Resolved ${conflicts.length} conflict(s) and ${label.toLowerCase()} ${branch}`)
+    await git.commitMerge(root)
+    spin.succeed(`Resolved ${conflicts.length} conflict(s) and merged ${branch}`)
   } catch (err) {
     const message = err instanceof Error ? err.message : String(err)
     spin.fail(message)
+    if (session) await vm.clearActivity(session.worktree, branch) // process.exit below skips finally
     await git.abortMerge(root)
     process.exit(1)
   } finally {
@@ -166,25 +188,6 @@ export async function mergeAndClose(branch: string, opts?: { squash?: boolean; f
   await git.deleteLocalBranch(branch, root).catch(() => {})
 }
 
-/** Generate a commit message for a squash-merge via Claude and commit. */
-async function squashCommit(branch: string, cwd: string): Promise<void> {
-  const diff = await git.diffStaged(cwd)
-
-  if (diff.trim()) {
-    const gen = await vm.claudePipe(
-      diff,
-      "Write a commit message summarizing all changes in this squash merge. Subject line: imperative mood, max 72 characters, no period. Add a blank line then a concise body with the key changes as bullet points. Output only the raw commit message, no quotes or markdown.",
-    )
-    if (gen.exitCode === 0 && gen.stdout.trim()) {
-      await git.commit(gen.stdout.trim(), cwd)
-      return
-    }
-  }
-
-  // Fallback if diff is empty or Claude fails
-  await git.commit(`squash ${branch}`, cwd)
-}
-
 /** Stage all changes, generate a commit message, and commit. Returns true on success. */
 export async function saveChanges(worktree: string, branch: string, message?: string): Promise<boolean> {
   const spin = spinner("Staging changes", branch)

src/commands/squash.ts

@@ -1,5 +1,67 @@
-import { mergeAndClose } from "./helpers.ts"
+import * as git from "../git.ts"
+import * as vm from "../vm.ts"
+import { spinner } from "../spinner.ts"
+import { die } from "../fmt.ts"
+import { requireSession } from "./helpers.ts"
 
-export async function action(branch: string, opts?: { force?: boolean }) {
-  await mergeAndClose(branch, { squash: true, force: opts?.force })
+export async function action(branch: string) {
+  const { session } = await requireSession(branch)
+  const worktree = session.worktree
+
+  if (await git.isDirty(worktree)) {
+    die(`Branch "${branch}" has unsaved changes. Run "sandlot save ${branch}" first.`)
+  }
+
+  const main = await git.mainBranch(worktree)
+
+  if (!await git.hasNewCommits(worktree)) {
+    die(`Branch "${branch}" has no commits beyond ${main}.`)
+  }
+
+  const base = await git.mergeBase(main, "HEAD", worktree)
+  const originalHead = await git.headRef(worktree)
+
+  const spin = spinner("Squashing", branch)
+  let didReset = false
+
+  try {
+    await git.resetSoft(base, worktree)
+    didReset = true
+
+    spin.text = "Starting container"
+    await vm.ensure((msg) => { spin.text = msg })
+
+    spin.text = "Generating commit message"
+    const diff = await git.diffStaged(worktree)
+
+    if (!diff.trim()) {
+      await git.resetSoft(originalHead, worktree).catch(() => {})
+      spin.fail("No changes after squash")
+      process.exit(1)
+    }
+
+    const gen = await vm.claudePipe(
+      diff,
+      "Write a commit message summarizing all changes. Subject line: imperative mood, max 72 characters, no period. Add a blank line then a concise body with the key changes as bullet points. Output only the raw commit message, no quotes or markdown.",
+    )
+
+    if (gen.exitCode !== 0 || !gen.stdout.trim()) {
+      spin.text = "AI commit message failed, using fallback"
+    }
+    const msg = (gen.exitCode === 0 && gen.stdout.trim()) || `squash ${branch}`
+    await git.commit(msg, worktree)
+
+    spin.succeed(`Squashed ${branch} into a single commit`)
+  } catch (err) {
+    const message = err instanceof Error ? err.message : String(err)
+    if (!didReset) {
+      spin.fail(`Squash failed: ${message}`)
+    } else {
+      const restored = await git.resetSoft(originalHead, worktree).then(() => true).catch(() => false)
+      spin.fail(restored
+        ? `Squash failed, changes restored: ${message}`
+        : `Squash failed and rollback failed — check "git reflog" in the worktree: ${message}`)
+    }
+    process.exit(1)
+  }
 }

src/git.ts

@@ -2,6 +2,12 @@ import { existsSync } from "fs"
 import { rm } from "fs/promises"
 import { $ } from "bun"
 
+/** Format a git error with a fallback for empty stderr. */
+function gitError(action: string, stderr: Buffer | string): Error {
+  const msg = stderr.toString().trim()
+  return new Error(`${action}: ${msg || "(no output)"}`)
+}
+
 /** Get the repo root from a working directory. */
 export async function repoRoot(cwd?: string): Promise<string> {
   const result = await $`git rev-parse --show-toplevel`.cwd(cwd ?? ".").nothrow().quiet()
@@ -72,7 +78,7 @@ export async function createWorktree(branch: string, worktreePath: string, cwd:
   }
   if (result.exitCode !== 0) {
     if (switchedFromBranch) await checkout(branch, cwd).catch(() => {})
-    throw new Error(`Failed to create worktree for "${branch}": ${result.stderr.toString().trim()}`)
+    throw gitError(`Failed to create worktree for "${branch}"`, result.stderr)
   }
   return { branchCreated: exists !== "local" }
 }
@@ -98,16 +104,13 @@ export async function deleteLocalBranch(branch: string, cwd: string): Promise<vo
 export async function checkout(branch: string, cwd: string): Promise<void> {
   const result = await $`git checkout ${branch}`.cwd(cwd).nothrow().quiet()
   if (result.exitCode !== 0) {
-    throw new Error(`Failed to checkout branch "${branch}": ${result.stderr.toString().trim()}`)
+    throw gitError(`Failed to checkout branch "${branch}"`, result.stderr)
   }
 }
 
 /** Merge a branch into the current branch. Returns conflicted file paths, or empty array if clean. */
-export async function merge(branch: string, cwd: string, opts?: { squash?: boolean }): Promise<string[]> {
-  const cmd = opts?.squash
-    ? $`git merge --squash ${branch}`.cwd(cwd).nothrow().quiet()
-    : $`git merge ${branch}`.cwd(cwd).nothrow().quiet()
-  const result = await cmd
+export async function merge(branch: string, cwd: string): Promise<string[]> {
+  const result = await $`git merge ${branch}`.cwd(cwd).nothrow().quiet()
   if (result.exitCode === 0) return []
 
   // Check for unmerged (conflicted) files
@@ -116,8 +119,7 @@ export async function merge(branch: string, cwd: string, opts?: { squash?: boole
   if (files.length > 0) return files
 
   // Not a conflict — some other merge failure
-  const label = opts?.squash ? "squash-merge" : "merge"
-  throw new Error(`Failed to ${label} branch "${branch}": ${result.stderr.toString().trim()}`)
+  throw gitError(`Failed to merge branch "${branch}"`, result.stderr)
 }
 
 /** Return the staged diff as text. */
@@ -129,20 +131,31 @@ export async function diffStaged(cwd: string): Promise<string> {
 export async function commit(message: string, cwd: string): Promise<void> {
   const result = await $`git commit -m ${message}`.cwd(cwd).nothrow().quiet()
   if (result.exitCode !== 0) {
-    throw new Error(`Failed to commit: ${result.stderr.toString().trim()}`)
+    throw gitError("Failed to commit", result.stderr)
+  }
+}
+
+/** Accept "theirs" version of a conflicted file. */
+export async function checkoutTheirs(file: string, cwd: string): Promise<void> {
+  const result = await $`git checkout --theirs -- ${file}`.cwd(cwd).nothrow().quiet()
+  if (result.exitCode !== 0) {
+    throw gitError(`Failed to checkout theirs for ${file}`, result.stderr)
   }
 }
 
 /** Stage a file. */
 export async function stageFile(file: string, cwd: string): Promise<void> {
-  await $`git add ${file}`.cwd(cwd).nothrow().quiet()
+  const result = await $`git add ${file}`.cwd(cwd).nothrow().quiet()
+  if (result.exitCode !== 0) {
+    throw gitError(`Failed to stage ${file}`, result.stderr)
+  }
 }
 
 /** Finalize a merge commit after resolving conflicts. */
 export async function commitMerge(cwd: string): Promise<void> {
   const result = await $`git commit --no-edit`.cwd(cwd).nothrow().quiet()
   if (result.exitCode !== 0) {
-    throw new Error(`Failed to commit merge: ${result.stderr.toString().trim()}`)
+    throw gitError("Failed to commit merge", result.stderr)
   }
 }
 
@@ -151,6 +164,23 @@ export async function abortMerge(cwd: string): Promise<void> {
   await $`git merge --abort`.cwd(cwd).nothrow().quiet()
 }
 
+/** Soft-reset to a given ref (keeps changes staged). */
+export async function resetSoft(ref: string, cwd: string): Promise<void> {
+  const result = await $`git reset --soft ${ref}`.cwd(cwd).nothrow().quiet()
+  if (result.exitCode !== 0) {
+    throw new Error(`Failed to reset to "${ref}": ${result.stderr.toString().trim()}`)
+  }
+}
+
+/** Get the full SHA of HEAD. */
+export async function headRef(cwd: string): Promise<string> {
+  const result = await $`git rev-parse HEAD`.cwd(cwd).nothrow().quiet()
+  if (result.exitCode !== 0) {
+    throw new Error("Could not resolve HEAD.")
+  }
+  return result.text().trim()
+}
+
 /** Rebase the current branch onto another. Returns conflicted file paths, or empty array if clean. */
 export async function rebase(onto: string, cwd: string): Promise<string[]> {
   // Bail early if a rebase is already in progress (check for rebase state directories, not REBASE_HEAD which can be stale)
@@ -181,7 +211,7 @@ export async function rebaseContinue(cwd: string): Promise<string[]> {
   const files = unmerged.trim().split("\n").filter(Boolean)
   if (files.length > 0) return files
 
-  throw new Error(`Rebase --continue failed: ${result.stderr.toString().trim()}`)
+  throw gitError("Rebase --continue failed", result.stderr)
 }
 
 /** Abort an in-progress rebase. */