Compute oldest timestamp for stashes including parent commit dates

(#4401, #4468)

Author: sergeibbb

CHANGELOG.md

@@ -8,6 +8,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/) and this p
 
 ### Fixed
 
+- Fixes stashes with parent commits older than the oldest stash not being visible on branches ([#4401](https://github.com/gitkraken/vscode-gitlens/issues/4401))
 - Fixes editing search result in Search & Compare view failure ([#4431](https://github.com/gitkraken/vscode-gitlens/issues/4431))
 
 ## [17.2.1] - 2025-06-26

src/env/node/git/sub-providers/stash.ts

@@ -166,7 +166,7 @@ export class StashGitSubProvider implements GitStashSubProvider {
 		// Create a copy because we are going to modify it and we don't want to mutate the cache
 		const stashes = new Map(stash.stashes);
 
-		const oldestStashDate = new Date(min(stash.stashes.values(), c => c.date.getTime())).toISOString();
+		const oldestStashDate = new Date(findOldestStashTimestamp(stash.stashes.values())).toISOString();
 
 		const result = await this.git.exec(
 			{ cwd: repoPath, cancellation: cancellation, errors: GitErrorHandling.Ignore },
@@ -481,3 +481,22 @@ function createStash(container: Container, s: ParsedStash, repoPath: string): Gi
 		onRef,
 	) as GitStashCommit;
 }
+
+/**
+ * Finds the oldest timestamp among stash commits and their parent commits.
+ * This includes both the stash commit dates and all parent commit timestamps (author and committer dates).
+ *
+ * @param stashes - Collection of stash commits to analyze
+ * @returns The oldest timestamp in milliseconds, or Infinity if no stashes provided
+ */
+export function findOldestStashTimestamp(stashes: Iterable<GitStashCommit>): number {
+	return min(stashes, c => {
+		return Math.min(
+			c.date.getTime(),
+			...(c.parentTimestamps
+				?.flatMap(p => [p.authorDate, p.committerDate])
+				.filter((x): x is number => x != null)
+				.map(x => x * 1000) ?? []),
+		);
+	});
+}