cleanups

README.md

@@ -72,10 +72,18 @@ PACKAGE_RELEASE=auto
 RUN_LINUX_TESTS=compile
 MAX_GLIBC_VERSION=2.34
 RELEASE_RETENTION=10
+PACKAGE_RETENTION=10
+CLEAN_BUILD_CACHE=1
 ```
 
 `RUN_LINUX_TESTS=compile` runs `cargo test --release --locked --no-run`. Use `full` to run the test suite or `0` to skip Rust tests.
 
+`PACKAGE_RETENTION=10` keeps at most the 10 newest DEB packages, 10 newest RHEL-family RPM packages, and 10 newest SUSE RPM packages in the published package pools. `RELEASE_RETENTION=10` separately controls atomic repository release directories.
+
+`CLEAN_BUILD_CACHE=1` removes the Cargo target directory after every build (successful or failed). Build output and package staging directories always live under `/tmp/rustbox-package-builder` and are removed after each build, so repeated compilations do not accumulate large compiler artifacts in `data/`. Set `CLEAN_BUILD_CACHE=0` only if you deliberately want to trade disk space for faster subsequent builds.
+
+On startup the builder also removes legacy `data/cargo/target`, `data/work/out`, and `data/work/package` directories created by older releases.
+
 All three supported Linux package families are built on every successful release. SUSE is not treated as a separate non-Linux target.
 
 ## Installed RustBox layout