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ceamac 7e1ee150f6 Add CLI option parsing and implement layer unmounting

Replace the implicit single-argument invocation with getopt_long-based
flags: -m/--mount (existing mount flow, now explicit), -u/--umount
(unmounts a layer via containers-storage), -t/--test (stub),
-l/--log-level (runtime spdlog level), -h/--help, -V/--version.
--mount now also prints the top layer's ID so it can be passed to
--umount.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

2026-08-10 09:03:58 +00:00

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CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project state

slocker-lite (C++20, built with Meson) mounts an OCI Image Layout tar (oci-layout + index.json + blobs/sha256/*, as produced by skopeo/podman save --format oci-archive/modern docker save) using containers-storage and fuse-overlayfs. Given an image tar path, it validates the layout, imports each layer into containers-storage's layer store in order (chained by parent), mounts the assembled top layer, and prints the resulting merged path. There is no README or broader architecture doc yet — treat this repo as still early-stage.

Source layout (all under src/):

main.cpp — CLI entry point, dependency checks, orchestration.
oci_image.{h,cpp} — validates/parses the OCI Image Layout tar (libarchive + nlohmann_json) and extracts layer blobs.
containers_storage.{h,cpp} — wraps the containers-storage CLI (import-layer, mount), forcing fuse-overlayfs as the overlay mount_program.
process.{h,cpp} — argv-based subprocess helper (fork/execvp/pipe, no shell).

Errors are logged via spdlog::error; every external command is also traced at debug level in run_process() (src/process.cpp) — visible via SPDLOG_LEVEL=debug, since spdlog's default level is info — and a failed external command additionally logs a spdlog::warn, which is visible by default (no env var needed). The final "mounted image at: ..." success line is direct stdout program output, not a log.

Because containers-storage mount runs rootless, the resulting mount lives in a private user+mount namespace; the printed path is only directly usable from within that same namespace (e.g. via containers-storage unshare), not from an arbitrary external shell.

Build & test commands

Build directory is buildDir/ (already configured).

Configure (only needed if buildDir/ is missing or deleted): meson setup buildDir
Build: meson compile -C buildDir (or ninja -C buildDir)
Run the executable: ./buildDir/slocker_lite -m <image.tar> (see --help for the full flag list: -m/--mount, -u/--umount, -t/--test, -l/--log-level, -h/--help, -V/--version)
Run tests: meson test -C buildDir

Code style

Null-pointer checks: prefer if (!ptr) / if (ptr) over if (ptr == nullptr) / if (ptr != nullptr).

Licensing

Every .c/.cpp/.h file under src/ must start with the GPLv2-or-later copyright header (see any existing file under src/ for the exact text).
After adding a new source file under src/, run ./add-license.sh from the repo root to prepend the header (it reads copyright-header and inserts it via sed, skipping files that already have it, so it's safe to re-run at any time).

Build configuration notes

meson.build sets warning_level=3 and cpp_std=c++20 — keep new code warning-clean under -Wall -Wextra -Wpedantic-equivalent settings.
The single Meson test() target runs slocker_lite against a fixture OCI image tar generated at build time by tests/gen_fixture.py (a custom_target) and checks its exit code (no test framework is wired in yet).

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