itest: Add output capture, metadata emission, proc macro, VM resource capping

Major feature expansion of the itest integration test framework to
make it reusable across bootc-dev projects (bcvk, composefs-rs, bootc).

Fork-exec output capture: when not under nextest or tmt, the harness
re-executes itself per test to capture stdout/stderr, preventing
interleaved output from parallel tests.

Test metadata: --emit-tmt and --emit-autopkgtest flags generate FMF
and DEP-8 metadata from registered tests, enabling tmt and autopkgtest
to discover and run individual tests.  Per-test TestMeta (timeout,
needs_root, isolation, tags, flaky, etc.) maps to format-specific
fields.  Verified end-to-end with tmt.

Proc macro: #[itest::test_attr] attribute macro replaces the
declarative macros.  Preserves doc comments, auto-converts error
types (anyhow/eyre compatible), detects async fn and wraps with a
tokio runtime, and accepts all metadata as attribute arguments.

VM resource capping: when no explicit --itype is set, itest detects
host memory (from /proc/meminfo and cgroup v2/v1 limits) and caps
the VM to 70% of available memory.  Prevents OOM on constrained CI
runners like GHA (7 GiB / 2 vCPU).  Override via ITEST_VM_MEMORY_MIB,
ITEST_VM_VCPUS, or ITEST_VM_MEMORY_FRACTION.

Spiked on composefs-rs: 43 tests migrated, net -120 lines deleted,
all tests pass.

Assisted-by: OpenCode (Claude Opus 4)
Signed-off-by: Colin Walters <walters@verbum.org>

Author: cgwalters

Cargo.lock

@@ -24,7 +24,8 @@ unit *ARGS:
 pull-test-images:
     podman pull -q {{ALL_BASE_IMAGES}} >/dev/null
 
-# Run integration tests (auto-detects nextest, with cleanup)
+# Run integration tests (prefers cargo-nextest, falls back to cargo test with
+# built-in fork-exec output capture)
 test-integration *ARGS: build pull-test-images
     #!/usr/bin/env bash
     set -euo pipefail
@@ -36,16 +37,15 @@ test-integration *ARGS: build pull-test-images
     # Clean up any leftover containers before starting
     cargo run --release --bin test-cleanup -p integration-tests 2>/dev/null || true
 
-    # Run the tests
+    # Prefer nextest for better UX (retries, timing, etc.), but the harness
+    # captures output itself via fork-exec so cargo test works too.
     if command -v cargo-nextest &> /dev/null; then
-        cargo nextest run --release -P integration -p integration-tests {{ ARGS }}
-        TEST_EXIT_CODE=$?
+        cargo nextest run --release -P integration -p integration-tests {{ ARGS }} && TEST_EXIT_CODE=0 || TEST_EXIT_CODE=$?
     else
-        cargo test --release -p integration-tests -- {{ ARGS }}
-        TEST_EXIT_CODE=$?
+        cargo test --release -p integration-tests -- {{ ARGS }} && TEST_EXIT_CODE=0 || TEST_EXIT_CODE=$?
     fi
 
-    # Clean up containers after tests complete
+    # Clean up containers after tests complete (must run even on failure)
     cargo run --release --bin test-cleanup -p integration-tests 2>/dev/null || true
 
     exit $TEST_EXIT_CODE

Justfile

@@ -0,0 +1,17 @@
+[package]
+name = "itest-macros"
+version = "0.1.0"
+edition = "2021"
+publish = false
+description = "Proc-macro companion crate for itest"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1"
+quote = "1"
+syn = { version = "2", features = ["full", "extra-traits"] }
+
+[lints]
+workspace = true