Ensure import by URL works after a failed import

If a project fails to import a project with one of the built-in
importers (e.g. GitHub, Bitbucket, GitLab project templates, etc.), a
user will be redirected to the `/import/new` page. The user can attempt
to import with a Git repository URL, but that would also fail because
`import_type` remained what it was set to initially
(e.g. `gitlab_project`). This caused `ImportService` to use the previous
importer instead of attempting to use the URL.

To fix this problem, we set `import_type` to `git` whenever the import
by URL parameters are used. This is mapped to a `nil` importer in
`Gitlab::ImportSources`.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/31589

app/controllers/concerns/import_url_params.rb

@@ -4,7 +4,13 @@ module ImportUrlParams
   def import_url_params
     return {} unless params.dig(:project, :import_url).present?
 
-    { import_url: import_params_to_full_url(params[:project]) }
+    {
+      import_url: import_params_to_full_url(params[:project]),
+      # We need to set import_type because attempting to retry an import by URL
+      # could leave a stale value around. This would erroneously cause an importer
+      # (e.g. import/export) to run.
+      import_type: 'git'
+    }
   end
 
   def import_params_to_full_url(params)

changelogs/unreleased/sh-fix-import-by-url-retries.yml

+---
+title: Ensure import by URL works after a failed import
+merge_request: 27546
+author:
+type: fixed

spec/controllers/concerns/import_url_params_spec.rb

@@ -31,7 +31,8 @@ describe ImportUrlParams do
     describe '#import_url_params' do
       it 'returns hash with import_url' do
         expect(import_url_params).to eq(
-          import_url: "https://user:password@url.com"
+          import_url: "https://user:password@url.com",
+          import_type: 'git'
         )
       end
     end
@@ -48,7 +49,8 @@ describe ImportUrlParams do
     describe '#import_url_params' do
       it 'does not change the url' do
         expect(import_url_params).to eq(
-          import_url: "https://user:password@url.com"
+          import_url: "https://user:password@url.com",
+          import_type: 'git'
         )
       end
     end