Git on main thread (#26573)

This moves spawning of the git subprocess to the main thread. We're not
yet
sure why, but when we spawn a process using GCD's background queues,
sub-processes like git-credential-manager fail to open windows.

This seems to be fixable either by using the main thread, or by using a
standard background thread,
but for now we use the main thread.


Release Notes:

- Git: Fix git-credential-manager

---------

Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
Co-authored-by: Kirill Bulatov <mail4score@gmail.com>

crates/git/src/commit.rs

@@ -3,20 +3,21 @@ use anyhow::{anyhow, Result};
 use collections::HashMap;
 use std::path::Path;
 
-pub fn get_messages(working_directory: &Path, shas: &[Oid]) -> Result<HashMap<Oid, String>> {
+pub async fn get_messages(working_directory: &Path, shas: &[Oid]) -> Result<HashMap<Oid, String>> {
     if shas.is_empty() {
         return Ok(HashMap::default());
     }
 
     const MARKER: &str = "<MARKER>";
 
-    let output = util::command::new_std_command("git")
+    let output = util::command::new_smol_command("git")
         .current_dir(working_directory)
         .arg("show")
         .arg("-s")
         .arg(format!("--format=%B{}", MARKER))
         .args(shas.iter().map(ToString::to_string))
         .output()
+        .await
         .map_err(|e| anyhow!("Failed to start git blame process: {}", e))?;
 
     anyhow::ensure!(