Edit UI text for Drupal Upgrade UI module

A first patch.
I didn't find anything more than the 2 suggestions, according to https://www.drupal.org/node/604342. Just one e.g. replaced by "for example", according to https://www.drupal.org/node/2637336.

I guess these 2 sentences are too long ?

• Table prefix field description :
  

  If more than one application will be sharing this database, a unique table name prefix – such as drupal_ – will prevent collisions.

• File Directory field description

To import files from your current Drupal site, enter a local file directory containing your site (e.g. /var/www/docroot), or your site address (e.g. http://example.com).

The Drupal Upgrade UI module also contain a useful quick link to the log messages related to migration:

/upgrade/log

Since it ends up at the Recent log messages page it doesn't get it's own menu item, but it would be nice to have it as a link in the UI text.

Tests should pass green.

@hauruck : I wonder where to add the message for #6. I suggest :
t('In case of errors or problems with the site, the Recent log messages page can be useful for debugging.', array(':dblog' => \Drupal::url('/upgrade/log')));

The text changes seem good to me, setting to RTBC, not sure if patch still applies.

Thanks for working on this!

+++ b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
@@ -702,7 +702,7 @@ public function buildOverviewForm(array $form, FormStateInterface $form_state) {
-        '#markup' => '<p>' . $this->t('Upgrade a Drupal site by importing it into a clean and empty new install of Drupal 8. You will lose any existing configuration once you import your site into it. See the <a href=":url">upgrading handbook</a> for more detailed information.', [
+        '#markup' => '<p>' . $this->t('Upgrade a site by importing it into a clean and empty new install of Drupal 8. You will lose any existing configuration once you import your site into it. See the <a href=":url">online documentation</a> for more detailed information.', [

+++ b/core/modules/migrate_drupal_ui/src/Tests/MigrateUpgradeTestBase.php
@@ -104,7 +104,7 @@ protected function tearDown() {
-    $this->assertText('Upgrade a Drupal site by importing it into a clean and empty new install of Drupal 8. You will lose any existing configuration once you import your site into it. See the upgrading handbook for more detailed information.');
+    $this->assertText('Upgrade a site by importing it into a clean and empty new install of Drupal 8. You will lose any existing configuration once you import your site into it. See the online documentation for more detailed information.');

I actually do not think this link text change is good; "online documentation" is not specific enough to accessibly describe where the link leads. It should probably be something like "online documentation for Drupal site upgrades". Note that this module is slightly a special case because the handbook we are linking is not for the individual module itself; it is general documentation on how to upgrade between major versions.

We had also discussed trying to replace the confusing terminology of "Upgrade" vs. "Update" entirely, but that is out of scope for this issue. See #2709507: [META] Remove outdated references to "upgrade" from core.

@hauruck, maybe you could create a separate issue for your suggestion from #6 and then mention it here? Also see the parent issue #2678638: [META] Usability refinements for Migrate UI for other work we are doing to improve this UI.

The other string cleanups in this patch look fine to me, especially as incremental improvements for the experimental module. Thanks!

An update according to #9 suggestion, at least the one that is in scope of this issue.

I reviewed the #10 patch file
I applied the patch
I can see the text is changed when I do a /upgrade

Since this only a text change I think this can be RTBC.

Thanks @scuba_fly for reviewing the patch!

This patch looks ready to me now. We can improve things further in #2678638: [META] Usability refinements for Migrate UI and #2709507: [META] Remove outdated references to "upgrade" from core.

Committed 8db2e4d and pushed to 8.2.x. Thanks!