Codex Reviewer

codex-rs/cli/src/main.rs

@@ -18,6 +18,8 @@ use codex_tui::Cli as TuiCli;
 use std::path::PathBuf;
 
 use crate::proto::ProtoCli;
+mod review;
+use review::ReviewCommand;
 
 /// Codex CLI
 ///
@@ -76,6 +78,9 @@ enum Subcommand {
     /// Internal: generate TypeScript protocol bindings.
     #[clap(hide = true)]
     GenerateTs(GenerateTsCommand),
+
+    /// Review the diff for merging one branch into another.
+    Review(ReviewCommand),
 }
 
 #[derive(Debug, Parser)]
@@ -212,6 +217,10 @@ async fn cli_main(codex_linux_sandbox_exe: Option<PathBuf>) -> anyhow::Result<()
         Some(Subcommand::GenerateTs(gen_cli)) => {
             codex_protocol_ts::generate_ts(&gen_cli.out_dir, gen_cli.prettier.as_deref())?;
         }
+        Some(Subcommand::Review(mut review_cli)) => {
+            prepend_config_flags(&mut review_cli.config_overrides, cli.config_overrides);
+            review::run_review_command(review_cli, codex_linux_sandbox_exe).await?;
+        }
     }
 
     Ok(())

codex-rs/cli/src/review.rs

@@ -0,0 +1,136 @@
+use clap::Parser;
+use codex_common::CliConfigOverrides;
+use codex_exec::Cli as ExecCli;
+use std::path::PathBuf;
+use tokio::process::Command;
+
+#[derive(Debug, Parser)]
+pub struct ReviewCommand {
+    #[clap(skip)]
+    pub config_overrides: CliConfigOverrides,
+
+    /// Branch merge spec in the form: source->target
+    #[arg(
+        value_name = "MERGE",
+        help = "Format: branch1->branch2 (source->target)",
+        required_unless_present = "target"
+    )]
+    pub merge_spec: Option<String>,
+
+    /// Source branch (defaults to current branch when omitted)
+    #[arg(long = "source", short = 's', value_name = "BRANCH")]
+    pub source: Option<String>,
+
+    /// Target branch (alternative to MERGE positional)
+    #[arg(
+        long = "target",
+        short = 't',
+        value_name = "BRANCH",
+        visible_alias = "into",
+        alias = "to"
+    )]
+    pub target: Option<String>,
+}
+
+pub async fn run_review_command(
+    cli: ReviewCommand,
+    codex_linux_sandbox_exe: Option<PathBuf>,
+) -> anyhow::Result<()> {
+    let ReviewCommand {
+        mut config_overrides,
+        merge_spec,
+        source,
+        target,
+    } = cli;
+
+    let (source, target) = match (source, target, merge_spec) {
+        (Some(s), Some(t), _) => (s, t),
+        (maybe_s, Some(t), None) => {
+            let s = match maybe_s {
+                Some(s) => s,
+                None => current_branch().await?,
+            };
+            (s, t)
+        }
+        (_, _, Some(spec)) => parse_merge_spec(&spec)?,
+        _ => unreachable!("clap should enforce required arguments"),
+    };
+
+    // Compute the patch representing merging `source` into `target`.
+    // Use the triple-dot diff to compare source against the merge base with target.
+    let patch = git_diff_patch(&target, &source).await?;
+
+    if patch.trim().is_empty() {
+        eprintln!("No differences found between {source} and {target}.");
+        return Ok(());
+    }
+
+    let prompt = build_review_prompt(&source, &target, &patch);
+
+    // Reuse the non-interactive exec runner with our constructed prompt.
+    // Build the default CLI via clap parsing to avoid reaching into private types.
+    let mut exec_cli = ExecCli::parse_from(["codex-exec", &prompt]);
+    exec_cli.config_overrides = std::mem::take(&mut config_overrides);
+
+    codex_exec::run_main(exec_cli, codex_linux_sandbox_exe).await
+}
+
+fn build_review_prompt(source: &str, target: &str, patch: &str) -> String {
+    let header = format!("You are reviewing a proposed merge of '{source}' into '{target}'.");
+    let instructions = "Please analyze the following git diff patch in detail. Provide: \n\
+        - 4 specific areas of improvement (actionable suggestions with rationale).\n\
+        - 4 thoughtful questions a senior software engineer would ask.\n\
+        Consider correctness, performance, security, readability, testing, and documentation.\n\
+        Structure the output with two sections: 'Areas of Improvement' (numbered 1-4) and 'Questions' (numbered 1-4).";
+    let diff_block = format!("```patch\n{patch}\n```\n");
+    format!("{header}\n\n{instructions}\n\n{diff_block}")
+}
+
+fn parse_merge_spec(spec: &str) -> anyhow::Result<(String, String)> {
+    let parts: Vec<&str> = spec.split("->").collect();
+    if parts.len() != 2 || parts[0].trim().is_empty() || parts[1].trim().is_empty() {
+        anyhow::bail!("Invalid merge spec: {spec}. Expected format: source->target");
+    }
+    Ok((parts[0].trim().to_string(), parts[1].trim().to_string()))
+}
+
+async fn git_diff_patch(target: &str, source: &str) -> anyhow::Result<String> {
+    // git diff target...source shows changes on source since the merge base with target.
+    let output = Command::new("git")
+        .arg("-c")
+        .arg("color.ui=never")
+        .arg("diff")
+        .arg("--no-ext-diff")
+        .arg("--patch")
+        .arg("--binary")
+        .arg("-M")
+        .arg("-C")
+        .arg(format!("{target}...{source}"))
+        .output()
+        .await?;
+
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        anyhow::bail!("Failed to compute git diff: {stderr}");
+    }
+
+    Ok(String::from_utf8_lossy(&output.stdout).to_string())
+}
+
+async fn current_branch() -> anyhow::Result<String> {
+    let output = Command::new("git")
+        .arg("rev-parse")
+        .arg("--abbrev-ref")
+        .arg("HEAD")
+        .output()
+        .await?;
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        anyhow::bail!("Failed to determine current branch: {stderr}");
+    }
+    let mut name = String::from_utf8_lossy(&output.stdout).trim().to_string();
+    if name.is_empty() || name == "HEAD" {
+        name = "HEAD".to_string();
+    }
+    Ok(name)
+}