Watcher: Watch for the HEAD SHA

Include the current HEAD commit SHA with GitActivity events emitted by the
watcher and propagate it through the API and frontend plumbing.

- Change GitActivity from a single ProjectId variant to a struct with
  project_id and head_sha so consumers can know the exact HEAD commit.
- When logs/HEAD changes, read the repository HEAD and peel to the commit
  to obtain the SHA, then emit GitActivity with head_sha.
- Surface head SHA to the frontend: include headSha in the ChangeForFrontend
  payload for git activity.
- Add gix and gitbutler-oxidize workspace deps used to access repository
  information.
- Expose head_sha API command and related response types; extend the
  existing operating_mode command to return head (shorthand) along with
  operating mode.
- Wire the new head_sha command into the server RPC dispatch and tauri
  command list.

This allows the UI and other consumers to reliably identify the current
commit when git activity updates occur.

Author: estib-vega

Cargo.lock

@@ -12,13 +12,50 @@ use tracing::instrument;
 
 use crate::error::Error;
 
+#[derive(Debug, serde::Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct HeadAndMode {
+    pub head: Option<String>,
+    pub operating_mode: Option<OperatingMode>,
+}
+
 #[api_cmd]
 #[cfg_attr(feature = "tauri", tauri::command(async))]
 #[instrument(err(Debug))]
-pub fn operating_mode(project_id: ProjectId) -> Result<OperatingMode, Error> {
+pub fn operating_mode(project_id: ProjectId) -> Result<HeadAndMode, Error> {
     let project = gitbutler_project::get(project_id)?;
     let ctx = CommandContext::open(&project, AppSettings::load_from_default_path_creating()?)?;
-    Ok(gitbutler_operating_modes::operating_mode(&ctx))
+    let head = match ctx.repo().head() {
+        Ok(head_ref) => head_ref.shorthand().map(|s| s.to_string()),
+        Err(_) => None,
+    };
+
+    Ok(HeadAndMode {
+        head,
+        operating_mode: Some(gitbutler_operating_modes::operating_mode(&ctx)),
+    })
+}
+
+#[derive(Debug, serde::Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct HeadSha {
+    head_sha: String,
+}
+
+#[api_cmd]
+#[cfg_attr(feature = "tauri", tauri::command(async))]
+#[instrument(err(Debug))]
+pub fn head_sha(project_id: ProjectId) -> Result<HeadSha, Error> {
+    let project = gitbutler_project::get(project_id)?;
+    let ctx = CommandContext::open(&project, AppSettings::load_from_default_path_creating()?)?;
+    let head_ref = ctx.repo().head().context("failed to get head")?;
+    let head_sha = head_ref
+        .peel_to_commit()
+        .context("failed to get head commit")?
+        .id()
+        .to_string();
+
+    Ok(HeadSha { head_sha })
 }
 
 #[api_cmd]

crates/but-api/src/commands/modes.rs

@@ -310,6 +310,7 @@ async fn handle_command(
         }
         // Operating modes commands
         "operating_mode" => modes::operating_mode_cmd(request.params),
+        "head_sha" => modes::head_sha_cmd(request.params),
         "enter_edit_mode" => modes::enter_edit_mode_cmd(request.params),
         "abort_edit_and_return_to_workspace" => {
             modes::abort_edit_and_return_to_workspace_cmd(request.params)

crates/but-server/src/lib.rs

@@ -65,9 +65,14 @@ impl ActiveProjects {
                         name: format!("project://{project_id}/git/head"),
                         payload: serde_json::json!({ "head": head, "operatingMode": operating_mode }),
                     },
-                    Change::GitActivity(project_id) => FrontendEvent {
+                    Change::GitActivity {
+                        project_id,
+                        head_sha,
+                    } => FrontendEvent {
                         name: format!("project://{project_id}/git/activity"),
-                        payload: serde_json::json!({}),
+                        payload: serde_json::json!({
+                            "headSha": head_sha,
+                        }),
                     },
                     Change::WorktreeChanges {
                         project_id,

crates/but-server/src/projects.rs

@@ -298,6 +298,7 @@ fn main() -> anyhow::Result<()> {
                 remotes::list_remotes,
                 remotes::add_remote,
                 modes::operating_mode,
+                modes::head_sha,
                 modes::enter_edit_mode,
                 modes::save_edit_and_return_to_workspace,
                 modes::abort_edit_and_return_to_workspace,

crates/gitbutler-tauri/src/main.rs

@@ -42,9 +42,14 @@ pub(crate) mod state {
                         payload: serde_json::json!({ "head": head, "operatingMode": operating_mode }),
                         project_id,
                     },
-                    Change::GitActivity(project_id) => ChangeForFrontend {
+                    Change::GitActivity {
+                        project_id,
+                        head_sha,
+                    } => ChangeForFrontend {
                         name: format!("project://{project_id}/git/activity"),
-                        payload: serde_json::json!({}),
+                        payload: serde_json::json!({
+                            "headSha": head_sha,
+                        }),
                         project_id,
                     },
                     Change::WorktreeChanges {

crates/gitbutler-tauri/src/window.rs

@@ -24,6 +24,8 @@ but-settings.workspace = true
 but-hunk-assignment.workspace = true
 but-hunk-dependency.workspace = true
 serde-error = "0.1.3"
+gix.workspace = true
+gitbutler-oxidize.workspace = true
 
 [lints.clippy]
 all = "deny"

crates/gitbutler-watcher/Cargo.toml

@@ -11,7 +11,10 @@ pub enum Change {
         head: String,
         operating_mode: OperatingMode,
     },
-    GitActivity(ProjectId),
+    GitActivity {
+        project_id: ProjectId,
+        head_sha: String,
+    },
     WorktreeChanges {
         project_id: ProjectId,
         changes: but_hunk_assignment::WorktreeChanges,

crates/gitbutler-watcher/src/events.rs

@@ -140,7 +140,17 @@ impl Handler {
                     self.emit_app_event(Change::GitFetch(ctx.project().id))?;
                 }
                 "logs/HEAD" => {
-                    self.emit_app_event(Change::GitActivity(ctx.project().id))?;
+                    let repo = ctx.repo();
+                    let head_ref = repo.head().context("failed to get head")?;
+                    let head_sha = head_ref
+                        .peel_to_commit()
+                        .context("failed to get head commit")?
+                        .id()
+                        .to_string();
+                    self.emit_app_event(Change::GitActivity {
+                        project_id: ctx.project().id,
+                        head_sha,
+                    })?;
                 }
                 "index" => {
                     let _ = self.emit_worktree_changes(ctx);