Url aliases migration part1.

Right now it straight migrate the aliases but the idea is that instead
of migrate the aliases migrate them as redirects only if the new site
url does not match with the old one.

web/modules/custom/geo_upgrade/migrations/upgrade_d7_url_alias.yml

@@ -0,0 +1,64 @@
+langcode: en
+status: true
+dependencies: {  }
+id: upgrade_d7_url_alias
+class: Drupal\migrate\Plugin\Migration
+field_plugin_method: null
+cck_plugin_method: null
+migration_tags:
+  - 'Drupal 7'
+  - Content
+migration_group: migrate_drupal_7_geo
+label: 'URL aliases'
+source:
+  plugin: d7_url_alias
+  constants:
+    slash: /
+process:
+  source:
+    -
+      plugin: concat
+      source:
+        - constants/slash
+        - source
+  alias:
+    -
+      plugin: skip_on_match
+      source: alias
+      method: row
+      # Content that wasn't migrated so the alias won't be migrate either.
+      value:
+        - 'event/' # Content type Event
+        - 'issue/' # Taxonomy vocabulary Issue
+        - 'regular-contributors/' # Regular contributors
+        - 'geo-volume-2/'
+        - 'geo-volume-3/'
+        - 'geo-volume-1/'
+        - 'ad-groups'
+    -
+      plugin: concat
+      source:
+        - constants/slash
+        - alias
+  langcode:
+    -
+      plugin: get
+      source: language
+#  node_translation:
+#    -
+#      plugin: explode
+#      source: source
+#      delimiter: /
+#    -
+#      plugin: extract
+#      default: INVALID_NID
+#      index:
+#        - 1
+#    -
+#      plugin: migration_lookup
+#      migration: {  }
+destination:
+  plugin: url_alias
+migration_dependencies:
+  required: {  }
+  optional: {  }

web/modules/custom/geo_upgrade/src/Plugin/migrate/process/SkipOnMatch.php

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+<?php
+
+namespace Drupal\geo_upgrade\Plugin\migrate\process;
+
+use Drupal\migrate_plus\Plugin\migrate\process\SkipOnValue;
+
+/**
+ * If the source evaluates to a configured value, skip processing or whole row.
+ *
+ * @MigrateProcessPlugin(
+ *   id = "skip_on_match"
+ * )
+ *  Similar to SkipOnValue but this just compare if part of the string match.
+ *
+ * @see \Drupal\migrate_plus\Plugin\migrate\process\SkipOnValue
+ */
+class SkipOnMatch extends  SkipOnValue {
+
+  /**
+   * Compare values to see if they are equal.
+   *
+   * @param mixed $value
+   *   Actual value.
+   * @param mixed $skipValue
+   *   Value to compare against.
+   * @param bool $equal
+   *   Compare as equal or not equal.
+   *
+   * @return bool
+   *   True if the compare successfully, FALSE otherwise.
+   */
+  protected function compareValue($value, $skipValue, $equal = TRUE) {
+    if ($equal) {
+      return strpos((string) $value, (string) $skipValue) !== FALSE;
+    }
+
+    return  strpos((string) $value, (string) $skipValue) === FALSE;
+  }
+
+}