Git context menu (#24844)

Adds the non-entry specific right click menu to the panel, and the
features contained therin:

* Stage all
* Discard Tracked Changes
* Trash Untracked Files

Also changes the naming from "Changes"/"New" to better match Git's
terminology (though not convinced on this, it was awkward to describe
"Discard Changes" without a way to distinguish between the changes and
the files containing them).

Release Notes:

- N/A

crates/git/src/git.rs

@@ -37,7 +37,8 @@ actions!(
         // editor::RevertSelectedHunks
         StageAll,
         UnstageAll,
-        RevertAll,
+        DiscardTrackedChanges,
+        TrashUntrackedFiles,
         Uncommit,
         Commit,
         ClearCommitMessage

crates/git/src/repository.rs

@@ -111,6 +111,7 @@ pub trait GitRepository: Send + Sync {
     fn branch_exits(&self, _: &str) -> Result<bool>;
 
     fn reset(&self, commit: &str, mode: ResetMode) -> Result<()>;
+    fn checkout_files(&self, commit: &str, paths: &[RepoPath]) -> Result<()>;
 
     fn show(&self, commit: &str) -> Result<CommitDetails>;
 
@@ -233,6 +234,31 @@ impl GitRepository for RealGitRepository {
         Ok(())
     }
 
+    fn checkout_files(&self, commit: &str, paths: &[RepoPath]) -> Result<()> {
+        if paths.is_empty() {
+            return Ok(());
+        }
+        let working_directory = self
+            .repository
+            .lock()
+            .workdir()
+            .context("failed to read git work directory")?
+            .to_path_buf();
+
+        let output = new_std_command(&self.git_binary_path)
+            .current_dir(&working_directory)
+            .args(["checkout", commit, "--"])
+            .args(paths.iter().map(|path| path.as_ref()))
+            .output()?;
+        if !output.status.success() {
+            return Err(anyhow!(
+                "Failed to checkout files:\n{}",
+                String::from_utf8_lossy(&output.stderr)
+            ));
+        }
+        Ok(())
+    }
+
     fn load_index_text(&self, path: &RepoPath) -> Option<String> {
         fn logic(repo: &git2::Repository, path: &RepoPath) -> Result<Option<String>> {
             const STAGE_NORMAL: i32 = 0;
@@ -617,6 +643,10 @@ impl GitRepository for FakeGitRepository {
         unimplemented!()
     }
 
+    fn checkout_files(&self, _: &str, _: &[RepoPath]) -> Result<()> {
+        unimplemented!()
+    }
+
     fn path(&self) -> PathBuf {
         let state = self.state.lock();
         state.path.clone()