Fix issue reporter "Preview on GitHub" opening repo root instead of the new-issue form

[ajasad25]

Fixes #319238
Fixes #318374

Problem

In the wizard issue reporter, "Preview on GitHub" builds a URL like
https://github.com/microsoft/vscode?title=…&body=… — the repository landing page with query params — instead of the new-issue form …/microsoft/vscode/issues/new?title=…. As a result the pre-filled title/body are dropped and the user lands on the repo home.

Cause

IssueFormService.getIssueUrlWithTitle only appended /issues/new when filing on an extension (fileOnExtension). For the VS Code / Marketplace targets it trusted that the target URL already ended in /issues/new. That holds for the normal path (product.reportIssueUrl = …/vscode/issues/new), but the wizard target can be a bare repo URL routed through data.uri (e.g. the Agents-window "Report Issue" flow and the "VS Code – Insiders" target), so the suffix was never added.

Fix

Generalize the /issues/new handling to apply to any GitHub target URL that doesn't already point at the new-issue form, and drop the now-redundant fileOnExtension argument:

if (this.isGitHubUrl(issueUrl) && !/\/issues\/new(?:[?#].*)?$/i.test(issueUrl)) {
    issueUrl = `${normalizeGitHubUrl(issueUrl)}/issues/new`;
}

• The !/\/issues\/new$/ check prevents double-appending for URLs that already target the form (e.g. the default product.reportIssueUrl, and extension URLs which getExtensionIssueUrl already normalizes), so already-correct flows are unchanged.
• The isGitHubUrl guard leaves non-GitHub external trackers untouched — and those already short-circuit as external links before this point.

Scope

This is intentionally limited to the new wizard reporter (IssueFormService), which is the UI both issues exercise. The legacy reporter (baseIssueReporterService) derives its VS Code target from product.reportIssueUrl (already …/issues/new) and does not consume data.uri, so it is not affected by these reports. Happy to extend the same hardening there if preferred.

Verification

• Simulated getIssueUrlWithTitle + normalizeGitHubUrl over the bug inputs and edge cases: bare …/vscode → …/vscode/issues/new?title=…; already-/issues/new URLs, trailing slash, and extension URLs are unchanged (no double-append).

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Removes the fileOnExtension parameter from getIssueUrlWithTitle and instead applies the /issues/new normalization to any GitHub URL, so that non-extension targets (VS Code core / Marketplace) with bare repo URLs also open the pre-filled issue form.

Changes:

• Drop the fileOnExtension argument at the call site.
• Replace the extension-only guard with isGitHubUrl(issueUrl) and document why.