Remove gc command (#31)

## Summary
- Remove the `gc` command which inappropriately ran `nix-collect-garbage
-d`
- nixy uses `nix build --out-link`, not `nix profile`, so there are no
nixy-specific generations to GC
- Added FAQ entry in README explaining how to clean up Nix store
manually
- Bump version to 0.1.5

## Rationale
The `gc` command was problematic because:
1. It ran `nix-collect-garbage -d` which affects ALL Nix profiles
system-wide
2. nixy doesn't create its own profile generations (uses `--out-link`
instead)
3. Users expecting nixy-scoped cleanup got system-wide cleanup instead

Users who want to clean up unused Nix store paths can run
`nix-collect-garbage -d` directly.

## Test plan
- [x] Run cargo test (59 tests pass)
- [x] `nixy --help` no longer shows gc command
- [x] Documentation updated (README.md and README_ja.md)

Closes #21

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

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: yusukeshib

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "nixy-rs"
-version = "0.1.5"
+version = "0.1.6"
 edition = "2021"
 rust-version = "1.80"
 description = "Homebrew-style wrapper for Nix using flake.nix"

README.md

@@ -143,7 +143,6 @@ Packages are installed globally and available in all terminal sessions.
 | `nixy search <query>` | | Search for packages |
 | `nixy upgrade [input...]` | | Upgrade all inputs or specific ones |
 | `nixy sync` | | Build environment from flake.nix (for new machines) |
-| `nixy gc` | | Clean up old package versions |
 
 ### Profile Management
 
@@ -274,6 +273,15 @@ Packages with non-free licenses (e.g., `graphite-cli`, `slack`) are allowed by d
 nixy install slack
 ```
 
+**How do I clean up old Nix store paths?**
+nixy doesn't provide a garbage collection command because it uses `nix build --out-link` instead of `nix profile`. To clean up unused Nix store paths, use the standard Nix command directly:
+
+```bash
+nix-collect-garbage -d
+```
+
+Note: This will clean up ALL unused Nix profiles and store paths on your system, not just nixy-related ones.
+
 ---
 
 ## Appendix

README_ja.md

@@ -127,7 +127,6 @@ nixy upgrade            # 全パッケージをアップグレード
 | `nixy search <query>` | | パッケージを検索 |
 | `nixy upgrade [input...]` | | 全 input または指定した input をアップグレード |
 | `nixy sync` | | flake.nix から環境をビルド（新しいマシン用） |
-| `nixy gc` | | 古いパッケージを削除 |
 
 ### プロファイル管理
 
@@ -258,6 +257,15 @@ nixy sync                                     # 古い状態を適用
 nixy install slack
 ```
 
+**古い Nix ストアパスをクリーンアップするには？**
+nixy は `nix profile` ではなく `nix build --out-link` を使用しているため、ガベージコレクションコマンドを提供していません。未使用の Nix ストアパスをクリーンアップするには、標準の Nix コマンドを直接使用してください：
+
+```bash
+nix-collect-garbage -d
+```
+
+注意：これは nixy 関連のものだけでなく、システム上のすべての未使用の Nix プロファイルとストアパスをクリーンアップします。
+
 ---
 
 ## 付録

src/cli.rs

@@ -38,9 +38,6 @@ pub enum Commands {
     /// Build environment from flake.nix and create symlink
     Sync(SyncArgs),
 
-    /// Garbage collect old generations
-    Gc,
-
     /// Output shell config (for eval in rc files)
     Config {
         /// Shell type (bash, zsh, fish)

src/commands/gc.rs

@@ -1,5 +1,4 @@
 pub mod config;
-pub mod gc;
 pub mod install;
 pub mod list;
 pub mod profile;

src/commands/mod.rs

@@ -30,7 +30,6 @@ fn main() {
         Commands::Search { query } => commands::search::run(&query),
         Commands::Upgrade(args) => commands::upgrade::run(&config, args),
         Commands::Sync(_) => commands::sync::run(&config),
-        Commands::Gc => commands::gc::run(),
         Commands::Config { shell } => commands::config::run(&shell),
         Commands::Profile(args) => commands::profile::run(&config, args),
         Commands::SelfUpgrade(args) => commands::self_upgrade::run(args.force),

src/main.rs

@@ -301,20 +301,6 @@ impl Nix {
             .map(String::from)
             .collect())
     }
-
-    /// Run garbage collection
-    pub fn gc() -> Result<()> {
-        let status = Command::new("nix-collect-garbage")
-            .arg("-d")
-            .status()
-            .map_err(|e| Error::NixCommand(e.to_string()))?;
-
-        if !status.success() {
-            return Err(Error::NixCommand("Garbage collection failed".to_string()));
-        }
-
-        Ok(())
-    }
 }
 
 #[cfg(test)]

src/nix.rs

@@ -393,29 +393,6 @@ fn test_search_requires_query() {
     assert!(!output.status.success());
 }
 
-// =============================================================================
-// GC command tests
-// =============================================================================
-
-#[test]
-fn test_gc_runs() {
-    // GC should run without error (even if nix gc does nothing)
-    let output = nixy_cmd().arg("gc").output().unwrap();
-    // May succeed or fail depending on nix availability
-    let stdout = String::from_utf8_lossy(&output.stdout);
-    let stderr = String::from_utf8_lossy(&output.stderr);
-    // Should at least attempt to run
-    assert!(
-        output.status.success()
-            || stdout.contains("garbage")
-            || stderr.contains("nix")
-            || stderr.contains("gc"),
-        "GC should attempt to run: stdout={}, stderr={}",
-        stdout,
-        stderr
-    );
-}
-
 // =============================================================================
 // Help content tests
 // =============================================================================
@@ -468,14 +445,6 @@ fn test_help_shows_sync_command() {
     assert!(stdout.contains("sync"));
 }
 
-#[test]
-fn test_help_shows_gc_command() {
-    let output = nixy_cmd().arg("--help").output().unwrap();
-    assert!(output.status.success());
-    let stdout = String::from_utf8_lossy(&output.stdout);
-    assert!(stdout.contains("gc"));
-}
-
 #[test]
 fn test_help_shows_config_command() {
     let output = nixy_cmd().arg("--help").output().unwrap();