Fix image URLs

[cotti]

Fixes #2190

On assembler builds, image URLs were not being adjusted to their final paths. We can access this information through the context's PositionalNavigation.

[reakaleek]

Would testing help verify this?

[Mpdreamz]

I think we can simplify this a bit using:

		if (context.Build.AssemblerBuild && context.TryFindDocument(fi) is MarkdownFile currentMarkdown)
		{
			// Acquire navigation-aware path
			if (context.PositionalNavigation.MarkdownNavigationLookup.TryGetValue(currentMarkdown, out var currentNavigation))
			{
				var uri = new Uri(new UriBuilder("http", "localhost", 80, currentNavigation.Url).Uri, url);
				newUrl = uri.AbsolutePath;
			}
			else
				context.EmitError($"Failed to acquire navigation for current markdown file '{currentMarkdown.FileName}' while resolving relative url '{url}'.");
		}

[reakaleek]

Would testing help verify this?

I took a stab at creating a appropriate test for this:

#2199

I was able to verify, that the test succeeds with your changes and fails without your changes.

[reakaleek]

What are your thoughts on the changes suggest by CodeQL?

[Mpdreamz]

A few of those codeql suggestions might not be relevant if we use the Uri approach I suggested

[cotti]

Let's get them in, then!

[reakaleek]

Let's get them in, then!

I think @Mpdreamz meant that with the Uri approach, you don't need the custom url combine method.

[cotti]

Ah. Adjusting here.