revlog tab graph method extraction

Extract update_graph_rows and gate behind is_graph_visible/ready.

Author: philocalyst

src/tabs/revlog.rs

@@ -60,7 +60,7 @@ enum LogSearch {
 	Results(LogSearchResult),
 }
 
-///
+/// Top-level revlog tab that ties together the commit list, details, and search.
 pub struct Revlog {
 	repo: RepoPathRef,
 	commit_details: CommitDetailsComponent,
@@ -135,35 +135,10 @@ impl Revlog {
 			self.list
 				.refresh_extend_data(self.git_log.extract_items()?);
 
-			let (slice, global_start) = self.list.get_loaded_slice();
-			if !slice.is_empty() {
-				let mut branch_tips = HashSet::new();
-				let mut head_id = None;
-
-				for (id, branches) in self.list.local_branches() {
-					branch_tips.insert(*id);
-					if head_id.is_none()
-						&& branches.iter().any(|b| {
-							b.local_details()
-								.is_some_and(|d| d.is_head)
-						}) {
-						head_id = Some(*id);
-					}
-				}
-				branch_tips
-					.extend(self.list.remote_branches().keys());
-
-				let stashes = HashSet::new();
-
-				if let Some(rows) = self.git_log.get_graph_rows(
-					&slice,
-					global_start,
-					&branch_tips,
-					&stashes,
-					head_id.as_ref(),
-				) {
-					self.list.set_graph_rows(rows);
-				}
+			if self.list.is_graph_visible()
+				&& !self.list.is_graph_ready()
+			{
+				self.update_graph_rows();
 			}
 
 			self.git_tags.request(Duration::from_secs(3), false)?;
@@ -182,6 +157,47 @@ impl Revlog {
 		Ok(())
 	}
 
+	/// Computes graph rows for the current commit window. Rows
+	/// don't depend on the selection
+	/// so its is skipped while
+	/// [`CommitList::is_graph_ready`] holds the bag.
+	fn update_graph_rows(&mut self) {
+		let (slice, global_start) = self.list.get_loaded_slice();
+		if slice.is_empty() {
+			return;
+		}
+
+		let head_id = self.list.local_branches().iter().find_map(
+			|(id, branches)| {
+				let has_head = branches.iter().any(|branch| {
+					branch.local_details().is_some_and(|b| b.is_head)
+				});
+				has_head.then_some(*id)
+			},
+		);
+
+		let branch_tips: HashSet<_> = self
+			.list
+			.local_branches()
+			.keys()
+			.chain(self.list.remote_branches().keys())
+			.copied()
+			.collect();
+
+		// TODO: include stashes (heh)
+		let stashes = HashSet::new();
+
+		if let Some(rows) = self.git_log.get_graph_rows(
+			&slice,
+			global_start,
+			&branch_tips,
+			&stashes,
+			head_id.as_ref(),
+		) {
+			self.list.set_graph_rows(rows);
+		}
+	}
+
 	///
 	pub fn update_git(
 		&mut self,