Initial commit: krust - container image build tool for Rust

krust builds container images for Rust applications without Docker:
- Builds static binaries using musl libc
- Creates minimal OCI container images
- Pushes to any OCI-compliant registry
- Outputs digest to stdout for composability

Inspired by ko.build for Go applications.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

src/cli/mod.rs

@@ -0,0 +1,53 @@
+use clap::{Parser, Subcommand};
+use std::path::PathBuf;
+
+#[derive(Parser)]
+#[command(name = "krust")]
+#[command(author, version, about, long_about = None)]
+pub struct Cli {
+    #[command(subcommand)]
+    pub command: Commands,
+
+    /// Enable verbose logging
+    #[arg(short, long, global = true)]
+    pub verbose: bool,
+}
+
+#[derive(Subcommand)]
+pub enum Commands {
+    /// Build a container image from a Rust application
+    Build {
+        /// Path to the Rust project directory
+        #[arg(value_name = "DIRECTORY")]
+        path: Option<PathBuf>,
+
+        /// Target image reference (overrides KRUST_REPO)
+        #[arg(short, long, env = "KRUST_IMAGE")]
+        image: Option<String>,
+
+        /// Target platform (e.g., linux/amd64, linux/arm64)
+        #[arg(long, default_value = "linux/amd64")]
+        platform: String,
+
+        /// Skip pushing the image to the registry after building
+        #[arg(long)]
+        no_push: bool,
+
+        /// Repository prefix (e.g., ghcr.io/username)
+        #[arg(long, env = "KRUST_REPO")]
+        repo: Option<String>,
+
+        /// Additional cargo build arguments
+        #[arg(last = true)]
+        cargo_args: Vec<String>,
+    },
+
+    /// Push a built image to a container registry
+    Push {
+        /// Image reference to push
+        image: String,
+    },
+
+    /// Show version information
+    Version,
+}