land: perf-spawn-without-fork

.alfonso/release-notes/next/perf-spawn-without-fork.md

@@ -0,0 +1 @@
+- Daemon CPU on macOS: formatters, checkers and git probes no longer fork the daemon (they start through posix_spawn), and the per-edit git root-commit probe is reused until the repository's git files change; forking a large multi-threaded daemon took every malloc lock and stalled allocation process-wide.

benchmarks/aft-search/slice-descriptors/land-perf-spawn-without-fork.json

@@ -0,0 +1,12 @@
+{
+  "targeted_mechanism": "none",
+  "kind": "harness",
+  "slice_class": "engine_unwired",
+  "fixtures": [
+    "crates/aft/tests/integration/tool_call_parity_test.rs"
+  ],
+  "fenced_files": [
+    "crates/aft/src/search_index.rs"
+  ],
+  "note": "The only fenced change caches the git root-commit probe used for artifact cache keys, invalidated by a stamp of the repository's git files; search inputs are unchanged. Ranking and routing are unchanged; benchmark rows must remain byte-identical."
+}

crates/aft/src/alias/mod.rs

@@ -785,6 +785,7 @@ pub fn head_tree_entries(repo_root: &Path) -> Result<Vec<TrackedPath>, AliasErro
         });
     }
     let output = crate::effective_path::new_command("git")
+        .build()
         .arg("-C")
         .arg(repo_root)
         .args(["ls-tree", "-r", "-z", "HEAD"])
@@ -920,6 +921,7 @@ fn git_filter_attributes(
     let started_at = Instant::now();
     let output = run_command_with_input(
         crate::effective_path::new_command("git")
+            .build()
             .arg("-C")
             .arg(repo_root)
             .args(["check-attr", "--cached", "-z", "--stdin", "filter"]),

crates/aft/src/commands/callgraph_borrowed.rs

@@ -597,6 +597,7 @@ fn git_paths(root: &Path, args: &[&str]) -> Option<HashSet<String>> {
         return None;
     }
     let mut child = crate::effective_path::new_command("git")
+        .build()
         .arg("-C")
         .arg(root)
         .args(args)

crates/aft/src/commands/configure.rs

@@ -1558,6 +1558,7 @@ fn detect_worktree_bridge(ctx: &AppContext, project_root: &Path) -> (bool, Optio
     #[cfg(test)]
     ctx.record_worktree_bridge_probe_spawn_for_test();
     let output = crate::effective_path::new_command("git")
+        .build()
         .arg("-C")
         .arg(project_root)
         .args([
@@ -7539,6 +7540,7 @@ thread_local! {
 
 fn view_git_changed_paths(root: &Path, max_examined: usize) -> Result<BTreeSet<Vec<u8>>, String> {
     let child = crate::effective_path::new_command("git")
+        .build()
         .arg("-C")
         .arg(root)
         .args([

crates/aft/src/commands/conflicts.rs

@@ -32,6 +32,7 @@ fn git_toplevel(base_path: &Path) -> Result<PathBuf, String> {
         return Err(crate::developer_tools::MISSING_DEVELOPER_TOOLS_REASON.to_string());
     }
     let output = crate::effective_path::new_command("git")
+        .build()
         .args(["rev-parse", "--show-toplevel"])
         .current_dir(working_dir)
         .output()
@@ -84,6 +85,7 @@ fn discover_conflicted_files(
     let mut unmerged_files = HashSet::new();
 
     let output = crate::effective_path::new_command("git")
+        .build()
         .args(["ls-files", "--unmerged", "-z"])
         .current_dir(&toplevel)
         .output()
@@ -110,6 +112,7 @@ fn discover_conflicted_files(
 
     let mut sweep_error = None;
     match crate::effective_path::new_command("git")
+        .build()
         .args(["grep", "-z", "-lE", r"^(<<<<<<< |>>>>>>> )"])
         .current_dir(&toplevel)
         .output()
@@ -560,12 +563,14 @@ line 6"#;
         .expect("write conflicted file");
 
         let init = crate::effective_path::new_command("git")
+            .build()
             .args(["init", "--quiet"])
             .current_dir(&repo)
             .status()
             .expect("run git init");
         assert!(init.success(), "git init failed: {init}");
         let add = crate::effective_path::new_command("git")
+            .build()
             .args(["add", "conflicted.txt"])
             .current_dir(&repo)
             .status()