feat(impact): add git diff impact reports

crates/graphiq-cli/src/main.rs

@@ -49,6 +49,22 @@ enum Commands {
         #[arg(long, default_value = "both")]
         direction: String,
     },
+    Impact {
+        #[arg(long, value_name = "PATH", default_value = ".")]
+        project: PathBuf,
+        #[arg(long, default_value = ".graphiq/graphiq.db")]
+        db: PathBuf,
+        #[arg(long)]
+        base: Option<String>,
+        #[arg(long)]
+        head: Option<String>,
+        #[arg(short, long, default_value_t = 2)]
+        depth: usize,
+        #[arg(short, long, default_value_t = 30)]
+        top: usize,
+        #[arg(long)]
+        json: bool,
+    },
     Status {
         #[arg(long, default_value = ".graphiq/graphiq.db")]
         db: PathBuf,
@@ -171,6 +187,23 @@ fn main() {
             depth,
             direction,
         } => cmd_blast(&symbol, &db, depth, &direction),
+        Commands::Impact {
+            project,
+            db,
+            base,
+            head,
+            depth,
+            top,
+            json,
+        } => cmd_impact(
+            &project,
+            &db,
+            base.as_deref(),
+            head.as_deref(),
+            depth,
+            top,
+            json,
+        ),
         Commands::Status { db } => cmd_status(&db),
         Commands::Reindex { path, db } => cmd_reindex(&path, &db),
         Commands::Subsystems { db, roles } => cmd_subsystems(&db, roles),
@@ -459,6 +492,58 @@ fn cmd_blast(symbol_name: &str, db_path: &std::path::Path, depth: usize, directi
     }
 }
 
+fn cmd_impact(
+    project_path: &std::path::Path,
+    db_path: &std::path::Path,
+    base: Option<&str>,
+    head: Option<&str>,
+    depth: usize,
+    top: usize,
+    json: bool,
+) {
+    let project = project_path
+        .canonicalize()
+        .unwrap_or_else(|_| project_path.to_path_buf());
+    let db_path = resolve_db(&project, db_path);
+
+    if !db_path.exists() {
+        eprintln!("database not found: {}", db_path.display());
+        eprintln!("run `graphiq index {}` first", project.display());
+        std::process::exit(1);
+    }
+
+    let db = open_db_or_exit(&db_path);
+    let source = match base {
+        Some(base) => graphiq_core::impact::ChangeSource::BaseRef {
+            base: base.to_string(),
+            head: head.unwrap_or("HEAD").to_string(),
+        },
+        None => graphiq_core::impact::ChangeSource::WorkingTree,
+    };
+    let options = graphiq_core::impact::ImpactOptions {
+        project_root: project,
+        db_path: Some(db_path),
+        source,
+        depth: depth.min(10),
+        top: top.min(200),
+    };
+
+    match graphiq_core::impact::analyze_git_impact(&db, options) {
+        Ok(report) if json => match serde_json::to_string_pretty(&report) {
+            Ok(text) => println!("{text}"),
+            Err(e) => {
+                eprintln!("error serializing impact report: {e}");
+                std::process::exit(1);
+            }
+        },
+        Ok(report) => println!("{}", graphiq_core::impact::format_impact_report(&report)),
+        Err(e) => {
+            eprintln!("impact analysis failed: {e}");
+            std::process::exit(1);
+        }
+    }
+}
+
 fn cmd_status(db_path: &std::path::Path) {
     if !db_path.exists() {
         eprintln!("database not found: {}", db_path.display());