OpenGrok /diff compatibility

src/routes/(opengrok-compat)/diff/[project]/[...file]/+page.server.ts

@@ -0,0 +1,43 @@
+import { escapeRegExp } from "$lib/regexp";
+import { projectToRepo } from "$lib/server/opengrok-compat";
+import { listRepositories } from "$lib/server/zoekt-list-repositories";
+import { error, redirect } from "@sveltejs/kit";
+
+export const load: import("./$types").PageServerLoad = async ({
+  url,
+  params: { file, project },
+  parent,
+  setHeaders,
+  fetch,
+}) => {
+  if (!file) {
+    throw error(404);
+  }
+  const revision = url.searchParams.get("r");
+  const convertedRepo = projectToRepo.get(project);
+
+  const result = await listRepositories(
+    {
+      query: `repo:^${escapeRegExp(convertedRepo ?? project)}$`,
+    },
+    fetch
+  );
+  if (result.kind === "error") {
+    throw new Error(`Failed to list repositories: ${result.error}`);
+  }
+
+  const repo = result.results.repositories[0];
+  const fileUrl = repo?.fileUrlTemplate
+    .replaceAll("{{.Version}}", revision ?? repo.branches[0].name)
+    .replaceAll("{{.Path}}", file);
+
+  setHeaders({
+    "cache-control": "no-store,must-revalidate",
+  });
+
+  if (fileUrl && (await parent()).preferences.openGrokInstantRedirect) {
+    throw redirect(301, fileUrl);
+  }
+
+  return { file, fileUrl };
+};

src/routes/(opengrok-compat)/diff/[project]/[...file]/+page.svelte

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+<script lang="ts">
+  import ExampleQuery from "$lib/example-query.svelte";
+  import Link from "$lib/link.svelte";
+  import { escapeRegExp } from "$lib/regexp";
+
+  export let data: import("./$types").PageData;
+</script>
+
+<section class="space-y-2 pt-2">
+  <h2 class="text-2xl text-center">Diff viewer</h2>
+  <p>
+    OpenGrok's diff viewer that was previously available at this URL is
+    unfortunately not supported in neogrok.
+  </p>
+  {#if data.fileUrl}
+    <p>
+      That being said, we've been able to produce a URL to view the file on its
+      home site. Head on over: <Link to={data.fileUrl}>{data.fileUrl}</Link>.
+    </p>
+  {:else}
+    <p>
+      Even more unfortunately, we've not been able to produce a URL to view the
+      file somewhere else. You can try searching for it and going from there:
+      <ExampleQuery query={`file:^${escapeRegExp(data.file)}$`} />.
+    </p>
+  {/if}
+</section>