From a9ac1c5e9e19a1e198399b92e21f26b3a8fcb5b6 Mon Sep 17 00:00:00 2001
From: Sebastian Thiel <sebastian.thiel@icloud.com>
Date: Thu, 9 Jan 2025 17:14:50 +0100
Subject: [PATCH] feat: add `env::git_shell()` to obtain the shell Git would be
 using.

This is particularly useful to execute Git hooks.
---
 gix-path/src/env/mod.rs    | 17 +++++++++++++++++
 gix-path/tests/path/env.rs |  7 +++++++
 2 files changed, 24 insertions(+)

diff --git a/gix-path/src/env/mod.rs b/gix-path/src/env/mod.rs
index 154a0d1ddfa..cdc092dcb25 100644
--- a/gix-path/src/env/mod.rs
+++ b/gix-path/src/env/mod.rs
@@ -28,6 +28,23 @@ pub fn installation_config_prefix() -> Option<&'static Path> {
     installation_config().map(git::config_to_base_path)
 }
 
+/// Return the shell that Git would prefer as login shell, the shell to execute Git commands from.
+///
+/// On Windows, this is the `bash.exe` bundled with it, and on Unix it's the shell specified by `SHELL`,
+/// or `None` if it is truly unspecified.
+pub fn login_shell() -> Option<&'static Path> {
+    static PATH: Lazy<Option<PathBuf>> = Lazy::new(|| {
+        if cfg!(windows) {
+            installation_config_prefix()
+                .and_then(|p| p.parent())
+                .map(|p| p.join("usr").join("bin").join("bash.exe"))
+        } else {
+            std::env::var_os("SHELL").map(PathBuf::from)
+        }
+    });
+    PATH.as_deref()
+}
+
 /// Return the name of the Git executable to invoke it.
 /// If it's in the `PATH`, it will always be a short name.
 ///
diff --git a/gix-path/tests/path/env.rs b/gix-path/tests/path/env.rs
index 69beb85b6e7..76a7666c59e 100644
--- a/gix-path/tests/path/env.rs
+++ b/gix-path/tests/path/env.rs
@@ -7,6 +7,13 @@ fn exe_invocation() {
     );
 }
 
+#[test]
+fn git_shell() {
+    assert!(gix_path::env::login_shell()
+        .expect("There should always be the notion of a shell used by git")
+        .exists());
+}
+
 #[test]
 fn installation_config() {
     assert_ne!(