Setup Phabricator import

This sets up all the basics for importing Phabricator tasks into
GitLab issues.

To import all tasks from a Phabricator instance into GitLab, we'll
import all of them into a new project that will have its repository
disabled.

The import is hooked into a regular ProjectImport setup, but similar
to the GitHub parallel importer takes care of all the imports itself.

In this iteration, we're importing each page of tasks in a separate
sidekiq job.

The first thing we do when requesting a new page of tasks is schedule
the next page to be imported. But to avoid deadlocks, we only allow a
single job per worker type to run at the same time.

For now we're only importing basic Issue information, this should be
extended to richer information.

2 files changed, 33 insertions, 0 deletions

diff --git a/doc/user/project/import/index.md b/doc/user/project/import/index.md
index ebbc5ca133b..119bbbfc70b 100644
--- a/doc/user/project/import/index.md
+++ b/doc/user/project/import/index.md
@@ -14,6 +14,7 @@
 1. [From repo by URL](repo_by_url.md)
 1. [By uploading a manifest file (AOSP)](manifest.md)
 1. [From Gemnasium](gemnasium.md)
+1. [From Phabricator](phabricator.md)
 
 In addition to the specific migration documentation above, you can import any
 Git repository via HTTP from the New Project page. Be aware that if the
diff --git a/doc/user/project/import/phabricator.md b/doc/user/project/import/phabricator.md
new file mode 100644
index 00000000000..4d1d99fd35b
--- /dev/null
+++ b/doc/user/project/import/phabricator.md
@@ -0,0 +1,32 @@
+# Import Phabricator tasks into a GitLab project
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/60562) in
+GitLab 12.0.
+
+GitLab allows you to import all tasks from a Phabricator instance into
+GitLab issues. The import creates a single project with the
+repository disabled.
+
+Currently, only the following basic fields are imported:
+
+- Title
+- Description
+- State (open or closed)
+- Created at
+- Closed at
+
+
+## Enabling this feature
+
+While this feature is incomplete, a feature flag is required to enable it so that
+we can gain early feedback before releasing it for everyone. To enable it:
+
+1. Enable Phabricator as an [import source](../../admin_area/settings/visibility_and_access_controls.md#import-sources) in the Admin area.
+
+  ``` {.ruby}
+  Feature.enable(:phabricator_import)
+  ```
+
+The [import
+source](../../admin_area/settings/visibility_and_access_controls.md#import-sources)
+also needs to be activated by an admin in the admin interface.