feat(cli): discover, build, and cache project binary metadata

[ElijahAhianyo]

Description

Add logic to cot-cli to discover a project binary and extract its metadata.
There are 3 cases:

Slow Path

The binary exists but has not been built.

When searching for a binary, we find its exact location by delegating that responsibility to cargo_metadata, which resolves the target directory location. cargo_metadata gives us the target dir path and all present binaries. We apply some heuristics to select the right binary. If multiple binaries are found, we hard-fail and prompt the user to disambiguate. Once we have the binary path, we build it via cargo build (since it does not exist for the slow path) at the user's request (via a --build flag), then obtain metadata from the binary. The metadata is then cached for faster subsequent runs.

Warm Path

The binary exists but has changed or been recompiled since our last run.

After obtaining the binary path as described in the slow path, we compare the binary's mtime against the value stored in the cache. In the warm path, they differ. We build the binary and obtain metadata.

Hot Path

Metadata has been cached and the binary has not been recompiled since the last run.

After obtaining the binary and checking the mtime diff, we find no change, so we safely assume no recompilation is necessary. We invoke the binary directly.

Type of change

• Bug fix
• New feature
• Documentation
• Refactor / cleanup
• Performance improvement
• Other (describe above)

[github-actions]

Bencher Report

Project	cot
Branch	elijah/cot-cli-proxy/stack-2-discovery
Testbed	github-ubuntu-latest

Click to view all benchmark results

Benchmark	Latency	Benchmark Result milliseconds (ms) (Result Δ%)	Upper Boundary milliseconds (ms) (Limit %)
empty_router/empty_router	📈 view plot 🚷 view threshold	15.44 ms (+65.13%) Baseline: 9.35 ms	17.77 ms (86.88%)
json_api/json_api	📈 view plot 🚷 view threshold	1.12 ms (+8.74%) Baseline: 1.03 ms	1.37 ms (82.07%)
nested_routers/nested_routers	📈 view plot 🚷 view threshold	1.06 ms (+9.63%) Baseline: 0.97 ms	1.26 ms (84.16%)
single_root_route/single_root_route	📈 view plot 🚷 view threshold	1.02 ms (+9.26%) Baseline: 0.93 ms	1.22 ms (83.22%)
single_root_route_burst/single_root_route_burst	📈 view plot 🚷 view threshold	17.13 ms (+1.73%) Baseline: 16.84 ms	21.47 ms (79.78%)

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