feat(aw-sync): v2 segment writer + manifest behind sync-v2 feature flag

.github/workflows/build.yml

@@ -35,6 +35,8 @@ jobs:
       run: cargo build --workspace --verbose
     - name: Run tests
       run: cargo test --workspace --verbose
+    - name: Run aw-sync v2 tests (sync-v2 feature)
+      run: cargo test -p aw-sync --features sync-v2 v2 --verbose
     - uses: actions/upload-artifact@v7
       with:
         # TODO: These binaries are debug builds

aw-sync/Cargo.toml

@@ -28,6 +28,10 @@ clap = { version = "4.1", features = ["derive"], optional = true }
 ctrlc = { version = "3.4.5", optional = true }
 rusqlite = { version = "0.30", features = ["bundled"], optional = true }
 
+# sync-v2 dependencies (optional)
+zstd = { version = "0.13", optional = true }
+sha2 = { version = "0.10", optional = true }
+
 aw-server = { path = "../aw-server" }
 aw-models = { path = "../aw-models" }
 aw-datastore = { path = "../aw-datastore" }
@@ -40,9 +44,13 @@ openssl = { version = "0.10.80", features = ["vendored"] }  # https://github.com
 jni = { version = "0.21", default-features = false }
 android_logger = "0.13"
 
+[target.'cfg(windows)'.dependencies]
+windows-sys = { version = "0.59", features = ["Win32_Storage_FileSystem", "Win32_Foundation"] }
+
 [dev-dependencies]
 tempfile = "3"
 
 [features]
 default = ["cli"]
 cli = ["clap", "ctrlc", "dep:rusqlite"]
+sync-v2 = ["dep:zstd", "dep:sha2"]

aw-sync/README.md

@@ -57,6 +57,16 @@ Working paths (bare `aw-sync sync`, Android) write:
 
 The default daemon still writes `~/ActivityWatchSync/{device_id}/test.db` (two levels). `aw-sync sync` and the Android app cannot see that file.
 
+#### Experimental v2 folder format (`sync-v2` feature)
+
+Building with `--features sync-v2` compiles a writer for the immutable-segment format (`devices/{device_id}/manifest.json` plus `{slug}.{generation}.jsonl.zst` segments). It is not wired into any command yet.
+
+The writer stages every file as `*.tmp` next to its final name and renames it into place, so a file syncer can ship a half-written temp file. Readers ignore unknown names, but tell your syncer to skip them too. For Syncthing, add this to the sync folder's `.stignore`:
+
+```txt
+(?d)*.tmp
+```
+
 ### Running from source
 
 If you want to run it from source, in the root of the repository run:

aw-sync/src/lib.rs

@@ -31,5 +31,8 @@ mod status;
 pub use status::run_status;
 mod util;
 
+#[cfg(feature = "sync-v2")]
+pub mod v2;
+
 #[cfg(target_os = "android")]
 pub mod android;