fix: preserve existing session backups

Author: skulidropek

packages/docker-git-session-sync/src/backup.ts

@@ -587,6 +587,13 @@ const runSessionUpload = (
     const uploadEntries = [...prepared.uploadEntries, buildReadmeUploadEntry(readmeRepoPath, readmePath)]
     logVerbose(verbose, output, `Uploading snapshot to ${backupRepo.fullName}:${context.snapshotRef}`)
     const uploadResult = uploadSnapshot(backupRepo, context.snapshotRef, manifest, uploadEntries, ghEnv)
+    if (!uploadResult.changed) {
+      output.out(`[session-backup] skipped: no new or changed chat transcripts (${summary.fileCount} files, ${formatBytes(summary.totalBytes)})`)
+      printGitStatus(output, context.gitStatus)
+      logVerbose(verbose, output, `[session-backup] No backup repo changes for ${backupRepo.fullName}:${context.snapshotRef}`)
+      updateUploadComment(context, ghEnv, output, { state: "skipped", message: "No new or changed chat transcripts." })
+      return 0
+    }
     output.out(`[session-backup] ok: ${context.source.commitSha.slice(0, 12)} (${summary.fileCount} files, ${formatBytes(summary.totalBytes)})`)
     printGitStatus(output, context.gitStatus)
     logVerbose(verbose, output, `[session-backup] Uploaded snapshot to ${backupRepo.fullName}:${context.snapshotRef}`)

packages/docker-git-session-sync/src/shell.ts

@@ -516,7 +516,7 @@ export const prepareUploadArtifacts = (
   return { uploadEntries, manifestFiles }
 }
 
-type GitTreeChange = {
+export type GitTreeChange = {
   readonly path: string
   readonly mode: "100644"
   readonly type: "blob"
@@ -533,25 +533,6 @@ const buildFileMapFromTreeEntries = (entries: ReadonlyArray<TreeEntry>): Map<str
   return fileMap
 }
 
-export const removeSnapshotTreeEntries = (
-  entries: ReadonlyArray<TreeEntry>,
-  snapshotRef: string
-): ReadonlyArray<TreeEntry> => {
-  const snapshotPrefix = `${snapshotRef}/`
-  return entries.filter((entry) => entry.path !== snapshotRef && !entry.path.startsWith(snapshotPrefix))
-}
-
-export const buildSnapshotDeleteTreeEntries = (
-  entries: ReadonlyArray<TreeEntry>,
-  snapshotRef: string,
-  desiredPaths: ReadonlySet<string>
-): ReadonlyArray<GitTreeChange> => {
-  const snapshotPrefix = `${snapshotRef}/`
-  return entries
-    .filter((entry) => entry.type !== "tree" && entry.path.startsWith(snapshotPrefix) && !desiredPaths.has(entry.path))
-    .map((entry) => ({ path: entry.path, mode: "100644", type: "blob", sha: null }))
-}
-
 const createGitBlob = (repoFullName: string, entry: UploadEntry, ghEnv: GhEnv): string => {
   const content = fs.readFileSync(entry.sourcePath)
   const result = ensureSuccess(
@@ -641,15 +622,13 @@ const updateGitRef = (repoFullName: string, branch: string, commitSha: string, g
 const isRefUpdateConflict = (result: CommandResult): boolean =>
   /409|Conflict|Reference update failed|fast[- ]forward/iu.test(`${result.stderr}\n${result.stdout}`)
 
-const buildUploadTreeChanges = (
+export const buildUploadTreeChanges = (
   repoFullName: string,
-  snapshotRef: string,
   existingEntries: ReadonlyArray<TreeEntry>,
   desiredEntries: ReadonlyArray<UploadEntry>,
   ghEnv: GhEnv
 ): ReadonlyArray<GitTreeChange> => {
   const existingFileMap = buildFileMapFromTreeEntries(existingEntries)
-  const desiredPaths = new Set(desiredEntries.map((entry) => entry.repoPath))
   const changes: Array<GitTreeChange> = []
   for (const entry of desiredEntries) {
     if (existingFileMap.get(entry.repoPath)?.sha === entry.blobSha) {
@@ -662,17 +641,27 @@ const buildUploadTreeChanges = (
       sha: createGitBlob(repoFullName, entry, ghEnv)
     })
   }
-  changes.push(...buildSnapshotDeleteTreeEntries(existingEntries, snapshotRef, desiredPaths))
   return changes
 }
 
+export const hasChangedUploadEntries = (
+  existingEntries: ReadonlyArray<TreeEntry>,
+  desiredEntries: ReadonlyArray<UploadEntry>
+): boolean => {
+  const existingFileMap = buildFileMapFromTreeEntries(existingEntries)
+  return desiredEntries.some((entry) => existingFileMap.get(entry.repoPath)?.sha !== entry.blobSha)
+}
+
+const isContentUploadEntry = (entry: UploadEntry): boolean =>
+  entry.type !== "readme" && entry.type !== "manifest"
+
 export const uploadSnapshot = (
   backupRepo: BackupRepo,
   snapshotRef: string,
   snapshotManifest: SnapshotManifest,
   uploadEntries: ReadonlyArray<UploadEntry>,
   ghEnv: GhEnv
-): { readonly commitSha: string; readonly manifestPath: string; readonly manifestUrl: string } => {
+): { readonly changed: boolean; readonly commitSha: string; readonly manifestPath: string; readonly manifestUrl: string } => {
   const uploadRoot = fs.mkdtempSync(path.join(os.tmpdir(), "session-backup-api-"))
   const manifestPath = `${snapshotRef}/manifest.json`
   const manifestTempPath = path.join(uploadRoot, "manifest.json")
@@ -691,15 +680,23 @@ export const uploadSnapshot = (
       if (currentTree.headSha === undefined) {
         throw new Error(`failed to resolve ${backupRepo.fullName}@${backupRepo.defaultBranch} head`)
       }
+      if (!hasChangedUploadEntries(currentTree.entries, uploadEntries.filter(isContentUploadEntry))) {
+        return {
+          changed: false,
+          commitSha: currentTree.headSha,
+          manifestPath,
+          manifestUrl: buildBlobUrl(backupRepo.fullName, backupRepo.defaultBranch, manifestPath)
+        }
+      }
       const changes = buildUploadTreeChanges(
         backupRepo.fullName,
-        snapshotRef,
         currentTree.entries,
         desiredEntries,
         ghEnv
       )
       if (changes.length === 0) {
         return {
+          changed: false,
           commitSha: currentTree.headSha,
           manifestPath,
           manifestUrl: buildBlobUrl(backupRepo.fullName, backupRepo.defaultBranch, manifestPath)
@@ -710,6 +707,7 @@ export const uploadSnapshot = (
       const updateResult = updateGitRef(backupRepo.fullName, backupRepo.defaultBranch, commitSha, ghEnv)
       if (updateResult.success) {
         return {
+          changed: true,
           commitSha,
           manifestPath,
           manifestUrl: buildBlobUrl(backupRepo.fullName, backupRepo.defaultBranch, manifestPath)

packages/docker-git-session-sync/tests/session-files.test.ts

@@ -13,12 +13,12 @@ import {
 import { collectSessionFiles, parseUploadContext, uploadFromContext, type Output } from "../src/backup.js"
 import { parseArgs } from "../src/cli.js"
 import {
-  buildSnapshotDeleteTreeEntries,
+  buildUploadTreeChanges,
   gitBlobShaForBuffer,
-  prepareUploadArtifacts,
-  removeSnapshotTreeEntries
+  hasChangedUploadEntries,
+  prepareUploadArtifacts
 } from "../src/shell.js"
-import type { TreeEntry } from "../src/types.js"
+import type { TreeEntry, UploadEntry } from "../src/types.js"
 
 const output: Output = {
   out: () => undefined,
@@ -121,15 +121,21 @@ describe("upload artifacts", () => {
   })
 })
 
-describe("snapshot tree replacement", () => {
-  it("removes only files under the exact current snapshot prefix", () => {
+describe("snapshot tree updates", () => {
+  it("keeps stale remote session files untouched", () => {
     const entries: ReadonlyArray<TreeEntry> = [
       {
         path: "org/repo/pr-230/current/.codex/sessions/old.jsonl",
         mode: "100644",
         type: "blob",
         sha: "old"
       },
+      {
+        path: "org/repo/pr-230/current/.codex/sessions/keep.jsonl",
+        mode: "100644",
+        type: "blob",
+        sha: "keep"
+      },
       {
         path: "org/repo/pr-230/current-old/.codex/sessions/keep.jsonl",
         mode: "100644",
@@ -149,50 +155,18 @@ describe("snapshot tree replacement", () => {
         sha: "keep-other-pr"
       }
     ]
-
-    expect(removeSnapshotTreeEntries(entries, "org/repo/pr-230/current").map((entry) => entry.path)).toEqual([
-      "org/repo/pr-230/current-old/.codex/sessions/keep.jsonl",
-      "org/repo/pr-230/2026-04-26/manifest.json",
-      "org/repo/pr-231/current/.codex/sessions/keep.jsonl"
-    ])
-  })
-
-  it("builds delete entries only for stale current snapshot files", () => {
-    const entries: ReadonlyArray<TreeEntry> = [
+    const desiredEntries: ReadonlyArray<UploadEntry> = [
       {
-        path: "org/repo/pr-230/current/.codex/sessions/old.jsonl",
-        mode: "100644",
-        type: "blob",
-        sha: "old"
-      },
-      {
-        path: "org/repo/pr-230/current/.codex/sessions/keep.jsonl",
-        mode: "100644",
-        type: "blob",
-        sha: "keep"
-      },
-      {
-        path: "org/repo/pr-230/current-old/.codex/sessions/old.jsonl",
-        mode: "100644",
-        type: "blob",
-        sha: "neighbor"
+        repoPath: "org/repo/pr-230/current/.codex/sessions/keep.jsonl",
+        sourcePath: path.join(tmpDir, "unused.jsonl"),
+        type: "file",
+        size: 4,
+        blobSha: "keep"
       }
     ]
 
-    expect(
-      buildSnapshotDeleteTreeEntries(
-        entries,
-        "org/repo/pr-230/current",
-        new Set(["org/repo/pr-230/current/.codex/sessions/keep.jsonl"])
-      )
-    ).toEqual([
-      {
-        path: "org/repo/pr-230/current/.codex/sessions/old.jsonl",
-        mode: "100644",
-        type: "blob",
-        sha: null
-      }
-    ])
+    expect(hasChangedUploadEntries(entries, desiredEntries)).toBe(false)
+    expect(buildUploadTreeChanges("backup-owner/docker-git-sessions", entries, desiredEntries, {})).toEqual([])
   })
 })