From 42a9f08bcb6e4042c47ac3b4734589a087ff4bb8 Mon Sep 17 00:00:00 2001
From: Remo Senekowitsch <remo@buenzli.dev>
Date: Mon, 13 Jan 2025 19:25:26 +0100
Subject: [PATCH] Make target dir self-ignoring

---
 src/cargo/core/workspace.rs | 11 +++++++++--
 src/cargo/ops/cargo_new.rs  |  4 ++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/cargo/core/workspace.rs b/src/cargo/core/workspace.rs
index a81c6b9304e..4ef1d70e9e3 100644
--- a/src/cargo/core/workspace.rs
+++ b/src/cargo/core/workspace.rs
@@ -402,9 +402,16 @@ impl<'gctx> Workspace<'gctx> {
     }
 
     pub fn target_dir(&self) -> Filesystem {
-        self.target_dir
+        let target_dir = self
+            .target_dir
             .clone()
-            .unwrap_or_else(|| self.default_target_dir())
+            .unwrap_or_else(|| self.default_target_dir());
+
+        let path = target_dir.as_path_unlocked();
+        paths::create_dir_all(path).unwrap();
+        std::fs::write(path.join(".gitignore"), "*\n").unwrap();
+
+        target_dir
     }
 
     fn default_target_dir(&self) -> Filesystem {
diff --git a/src/cargo/ops/cargo_new.rs b/src/cargo/ops/cargo_new.rs
index 88d2d6bf162..2ea18513285 100644
--- a/src/cargo/ops/cargo_new.rs
+++ b/src/cargo/ops/cargo_new.rs
@@ -680,6 +680,10 @@ fn write_ignore_file(base_path: &Path, list: &IgnoreList, vcs: VersionControl) -
     }
 
     for fp_ignore in match vcs {
+        // TODO: Stop writing the .gitignore file by default once enough
+        // time has passed. The target directory generated by cargo is now
+        // self-ignoring, but the .gitignore file should still be generated
+        // while people are still using older toolchains.
         VersionControl::Git => vec![base_path.join(".gitignore")],
         VersionControl::Hg => vec![base_path.join(".hgignore")],
         VersionControl::Pijul => vec![base_path.join(".ignore")],