docs: add README, MIT LICENSE, and clippy/linting notes to AGENTS.md

AGENTS.md

@@ -13,10 +13,14 @@
 - Run help: `cargo run -- --help`.
 - Parse DER file: `cargo run -- --file tests/data/test.cert.der --input-format der`.
 - Parse hex string: `cargo run -- 3082...` (whitespace allowed; auto-detected).
-- Lint: `cargo clippy -- -D warnings`.
+- Lint: `cargo clippy --all-targets -- -D warnings`.
 - Format: `cargo fmt`.
 - Tests: `cargo test`.
 
+## Linting & Defaults
+- Clippy: configured via `clippy.toml`; we keep warnings at deny to avoid regressions.
+- BIT STRINGs: truncated by default for readability (bits: 128, hex bytes: 16). Override with `--bits-truncate` or `--bits-truncate-bytes`.
+
 ## Coding Style & Naming Conventions
 - Rust 2021; 4-space indent; `rustfmt` defaults (`cargo fmt`).
 - Naming: modules `snake_case`; types/enums `CamelCase`; functions `snake_case`; constants `SCREAMING_SNAKE_CASE`.

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2025 asn1parse contributors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -0,0 +1,37 @@
+## asn1parse
+
+A tiny Rust CLI to pretty‑print DER‑encoded ASN.1 structures. It uses yasna for DER parsing and prints a readable tree with optional ANSI colors. Helpful for inspecting X.509 certificates and general DER blobs.
+
+### Features
+- Generic DER pretty‑printer with colorized types.
+- Heuristics: decodes nested DER inside OCTET/Bit Strings.
+- Friendly outputs for common X.509 bits (SAN names, iPAddress, keyUsage summary).
+- Sensible defaults: BIT STRINGs are truncated for readability (bits=128, hex bytes=16) and marked with an ellipsis and “(truncated)”.
+
+### Install
+- Build: `cargo build --release`
+- Run help: `cargo run -- --help`
+
+### Usage
+- Parse DER file: `cargo run -- --file tests/data/test.cert.der --input-format der --color never`
+- Parse hex string: `cargo run -- "3006020101020102"`
+- Force hex view for bit strings: `cargo run -- 030300DEAD --bits-format hex`
+- Override truncation: `--bits-truncate 256` or `--bits-truncate-bytes 32`
+
+### Development
+- Lint: `cargo clippy --all-targets -- -D warnings` (configured via `clippy.toml`)
+- Format: `cargo fmt`
+- Test: `cargo test`
+
+### Generating a sample certificate
+- Generate rich test cert (SAN, keyUsage, policies, constraints):
+  - `openssl req -new -newkey rsa:2048 -nodes -keyout tests/data/rich.key.pem -x509 -days 7 -config tests/data/openssl-rich.cnf -out tests/data/rich.cert.pem`
+  - `openssl x509 -in tests/data/rich.cert.pem -outform der -out tests/data/rich.cert.der`
+- View: `cargo run -- --file tests/data/rich.cert.der --input-format der --color never`
+
+### Notes
+- Binary DER via stdin is not supported in text mode; use `--file` or provide hex on stdin.
+- Colors auto‑detect TTY; use `--color always` to force.
+
+### License
+MIT — see `LICENSE`.