Fixes #2394 ensures uncommitted parent is HEAD

CHANGELOG.md

@@ -39,6 +39,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/) and this p
 
 ### Fixed
 
+- Fixes [#2394](https://github.com/gitkraken/vscode-gitlens/issues/2394) - Work in progress file diff compares working tree with working tree, instead of working tree with head
 - Fixes [#2207](https://github.com/gitkraken/vscode-gitlens/issues/2207) - Error when trying to push individual commit
 - Fixes [#2301](https://github.com/gitkraken/vscode-gitlens/issues/2301) - Create Worktree button doesn't work in certain cases
 - Fixes [#2382](https://github.com/gitkraken/vscode-gitlens/issues/2382) - commits disappearing from commit details view when they shouldn't

src/git/gitProviderService.ts

@@ -2303,6 +2303,10 @@ export class GitProviderService implements Disposable {
 		pathOrUri?: string | Uri,
 		options?: { timeout?: number },
 	) {
+		if (pathOrUri != null && GitRevision.isUncommittedParent(ref)) {
+			ref = 'HEAD';
+		}
+
 		if (
 			!ref ||
 			ref === GitRevision.deletedOrMissing ||

src/git/models/commit.ts

@@ -173,9 +173,11 @@ export class GitCommit implements GitRevisionReference {
 
 	private _resolvedPreviousSha: string | undefined;
 	get unresolvedPreviousSha(): string {
-		return (
-			this._resolvedPreviousSha ?? (this.file != null ? this.file.previousSha : this.parents[0]) ?? `${this.sha}^`
-		);
+		const previousSha =
+			this._resolvedPreviousSha ??
+			(this.file != null ? this.file.previousSha : this.parents[0]) ??
+			`${this.sha}^`;
+		return GitRevision.isUncommittedParent(previousSha) ? 'HEAD' : previousSha;
 	}
 
 	private _etagFileSystem: number | undefined;

src/git/models/reference.ts

@@ -47,6 +47,10 @@ export namespace GitRevision {
 		return ref === uncommitted || ref === uncommittedStaged || (!exact && isMatch(uncommittedRegex, ref));
 	}
 
+	export function isUncommittedParent(ref: string | undefined) {
+		return ref === `${uncommitted}^` || ref === `${uncommittedStaged}^`;
+	}
+
 	export function isUncommittedStaged(ref: string | undefined, exact: boolean = false): boolean {
 		return ref === uncommittedStaged || (!exact && isMatch(uncommittedStagedRegex, ref));
 	}