From 1661e4b5e1d8ebfef28f798fcb86ba2656373ba0 Mon Sep 17 00:00:00 2001
From: Dimitar Gyurov <dgyurov@gmail.com>
Date: Fri, 10 Mar 2023 23:42:42 +0100
Subject: [PATCH] Add a version-control statusline element (#5682)

---
 Cargo.lock                      |  1 +
 book/src/configuration.md       |  1 +
 helix-term/src/ui/statusline.rs | 14 ++++++++++++++
 helix-vcs/Cargo.toml            |  1 +
 helix-vcs/src/git.rs            | 17 +++++++++++++++++
 helix-vcs/src/lib.rs            | 14 +++++++++++++-
 helix-view/src/document.rs      | 16 ++++++++++++++++
 helix-view/src/editor.rs        |  4 ++++
 8 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/Cargo.lock b/Cargo.lock
index a1a9eae4d..de985bca1 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1212,6 +1212,7 @@ dependencies = [
 name = "helix-vcs"
 version = "0.6.0"
 dependencies = [
+ "arc-swap",
  "gix",
  "helix-core",
  "imara-diff",
diff --git a/book/src/configuration.md b/book/src/configuration.md
index 4b62ca521..e698646bc 100644
--- a/book/src/configuration.md
+++ b/book/src/configuration.md
@@ -111,6 +111,7 @@ The following statusline elements can be configured:
 | `position-percentage` | The cursor position as a percentage of the total number of lines |
 | `separator` | The string defined in `editor.statusline.separator` (defaults to `"│"`) |
 | `spacer` | Inserts a space between elements (multiple/contiguous spacers may be specified) |
+| `version-control` | The current branch name or detached commit hash of the opened workspace |
 
 ### `[editor.lsp]` Section
 
diff --git a/helix-term/src/ui/statusline.rs b/helix-term/src/ui/statusline.rs
index 3e7065b82..887863519 100644
--- a/helix-term/src/ui/statusline.rs
+++ b/helix-term/src/ui/statusline.rs
@@ -159,6 +159,7 @@ where
         helix_view::editor::StatusLineElement::TotalLineNumbers => render_total_line_numbers,
         helix_view::editor::StatusLineElement::Separator => render_separator,
         helix_view::editor::StatusLineElement::Spacer => render_spacer,
+        helix_view::editor::StatusLineElement::VersionControl => render_version_control,
     }
 }
 
@@ -476,3 +477,16 @@ where
 {
     write(context, String::from(" "), None);
 }
+
+fn render_version_control<F>(context: &mut RenderContext, write: F)
+where
+    F: Fn(&mut RenderContext, String, Option<Style>) + Copy,
+{
+    let head = context
+        .doc
+        .version_control_head()
+        .unwrap_or_default()
+        .to_string();
+
+    write(context, head, None);
+}
diff --git a/helix-vcs/Cargo.toml b/helix-vcs/Cargo.toml
index 789ee7951..58c078b43 100644
--- a/helix-vcs/Cargo.toml
+++ b/helix-vcs/Cargo.toml
@@ -15,6 +15,7 @@ helix-core = { version = "0.6", path = "../helix-core" }
 
 tokio = { version = "1", features = ["rt", "rt-multi-thread", "time", "sync", "parking_lot", "macros"] }
 parking_lot = "0.12"
+arc-swap = { version = "1.6.0" }
 
 gix = { version = "0.39.0", default-features = false , optional = true }
 imara-diff = "0.1.5"
diff --git a/helix-vcs/src/git.rs b/helix-vcs/src/git.rs
index 2a540c8d1..1732bdd0d 100644
--- a/helix-vcs/src/git.rs
+++ b/helix-vcs/src/git.rs
@@ -1,4 +1,6 @@
+use arc_swap::ArcSwap;
 use std::path::Path;
+use std::sync::Arc;
 
 use gix::objs::tree::EntryMode;
 use gix::sec::trust::DefaultForLevel;
@@ -87,6 +89,21 @@ impl DiffProvider for Git {
         }
         Some(data)
     }
+
+    fn get_current_head_name(&self, file: &Path) -> Option<Arc<ArcSwap<Box<str>>>> {
+        debug_assert!(!file.exists() || file.is_file());
+        debug_assert!(file.is_absolute());
+        let repo = Git::open_repo(file.parent()?, None)?.to_thread_local();
+        let head_ref = repo.head_ref().ok()?;
+        let head_commit = repo.head_commit().ok()?;
+
+        let name = match head_ref {
+            Some(reference) => reference.name().shorten().to_string(),
+            None => head_commit.id.to_hex_with_len(8).to_string(),
+        };
+
+        Some(Arc::new(ArcSwap::from_pointee(name.into_boxed_str())))
+    }
 }
 
 /// Finds the object that contains the contents of a file at a specific commit.
diff --git a/helix-vcs/src/lib.rs b/helix-vcs/src/lib.rs
index 97320d325..6f5e40d0c 100644
--- a/helix-vcs/src/lib.rs
+++ b/helix-vcs/src/lib.rs
@@ -1,4 +1,5 @@
-use std::path::Path;
+use arc_swap::ArcSwap;
+use std::{path::Path, sync::Arc};
 
 #[cfg(feature = "git")]
 pub use git::Git;
@@ -18,6 +19,7 @@ pub trait DiffProvider {
     /// The data is returned as raw byte without any decoding or encoding performed
     /// to ensure all file encodings are handled correctly.
     fn get_diff_base(&self, file: &Path) -> Option<Vec<u8>>;
+    fn get_current_head_name(&self, file: &Path) -> Option<Arc<ArcSwap<Box<str>>>>;
 }
 
 #[doc(hidden)]
@@ -26,6 +28,10 @@ impl DiffProvider for Dummy {
     fn get_diff_base(&self, _file: &Path) -> Option<Vec<u8>> {
         None
     }
+
+    fn get_current_head_name(&self, _file: &Path) -> Option<Arc<ArcSwap<Box<str>>>> {
+        None
+    }
 }
 
 pub struct DiffProviderRegistry {
@@ -38,6 +44,12 @@ impl DiffProviderRegistry {
             .iter()
             .find_map(|provider| provider.get_diff_base(file))
     }
+
+    pub fn get_current_head_name(&self, file: &Path) -> Option<Arc<ArcSwap<Box<str>>>> {
+        self.providers
+            .iter()
+            .find_map(|provider| provider.get_current_head_name(file))
+    }
 }
 
 impl Default for DiffProviderRegistry {
diff --git a/helix-view/src/document.rs b/helix-view/src/document.rs
index db12fb92b..b2a9ddec4 100644
--- a/helix-view/src/document.rs
+++ b/helix-view/src/document.rs
@@ -1,5 +1,6 @@
 use anyhow::{anyhow, bail, Context, Error};
 use arc_swap::access::DynAccess;
+use arc_swap::ArcSwap;
 use futures_util::future::BoxFuture;
 use futures_util::FutureExt;
 use helix_core::auto_pairs::AutoPairs;
@@ -158,6 +159,7 @@ pub struct Document {
     language_server: Option<Arc<helix_lsp::Client>>,
 
     diff_handle: Option<DiffHandle>,
+    version_control_head: Option<Arc<ArcSwap<Box<str>>>>,
 }
 
 use std::{fmt, mem};
@@ -404,6 +406,7 @@ impl Document {
             language_server: None,
             diff_handle: None,
             config,
+            version_control_head: None,
         }
     }
     pub fn default(config: Arc<dyn DynAccess<Config>>) -> Self {
@@ -707,6 +710,8 @@ impl Document {
             None => self.diff_handle = None,
         }
 
+        self.version_control_head = provider_registry.get_current_head_name(&path);
+
         Ok(())
     }
 
@@ -1158,6 +1163,17 @@ impl Document {
         }
     }
 
+    pub fn version_control_head(&self) -> Option<Arc<Box<str>>> {
+        self.version_control_head.as_ref().map(|a| a.load_full())
+    }
+
+    pub fn set_version_control_head(
+        &mut self,
+        version_control_head: Option<Arc<ArcSwap<Box<str>>>>,
+    ) {
+        self.version_control_head = version_control_head;
+    }
+
     #[inline]
     /// Tree-sitter AST tree
     pub fn syntax(&self) -> Option<&Syntax> {
diff --git a/helix-view/src/editor.rs b/helix-view/src/editor.rs
index 1b4664ffb..41aa707f2 100644
--- a/helix-view/src/editor.rs
+++ b/helix-view/src/editor.rs
@@ -467,6 +467,9 @@ pub enum StatusLineElement {
 
     /// A single space
     Spacer,
+
+    /// Current version control information
+    VersionControl,
 }
 
 // Cursor shape is read and used on every rendered frame and so needs
@@ -1297,6 +1300,7 @@ impl Editor {
             if let Some(diff_base) = self.diff_providers.get_diff_base(&path) {
                 doc.set_diff_base(diff_base, self.redraw_handle.clone());
             }
+            doc.set_version_control_head(self.diff_providers.get_current_head_name(&path));
 
             let id = self.new_document(doc);
             let _ = self.launch_language_server(id);