Add documentation regarding rake task

doc/administration/raketasks/uploads/migrate.md

@@ -7,10 +7,32 @@ After [configuring the object storage](../../uploads.md#using-object-storage) fo
 >**Note:**
 All of the processing will be done in a background worker and requires **no downtime**.
 
-This tasks uses 3 parameters to find uploads to migrate.
+### All-in-one rake task
+
+GitLab provides a wrapper rake task that migrates all uploaded files - avatars,
+logos, attachments, favicon, etc. - to object storage in one go. Under the hood,
+it invokes individual rake tasks to migrate files falling under each of this
+category one by one. The specifications of these individual rake tasks are
+described in the next section.
+
+**Omnibus Installation**
+
+```bash
+gitlab-rake "gitlab:uploads:migrate:all"
+```
+
+**Source Installation**
+
+```bash
+sudo RAILS_ENV=production -u git -H bundle exec rake gitlab:uploads:migrate:all
+```
+
+### Individual rake tasks
 
 >**Note:**
-These parameters are mainly internal to GitLab's structure, you may want to refer to the task list instead below.
+If you already ran the rake task mentioned above, no need to run these individual rake tasks as that has been done automatically.
+
+The rake task uses 3 parameters to find uploads to migrate.
 
 Parameter | Type | Description
 --------- | ---- | -----------
@@ -18,6 +40,9 @@ Parameter | Type | Description
 `model_class` | string | Type of the model to migrate from
 `mount_point` | string/symbol | Name of the model's column on which the uploader is mounted on.
 
+>**Note:**
+These parameters are mainly internal to GitLab's structure, you may want to refer to the task list instead below.
+
 This task also accepts some environment variables which you can use to override
 certain values:
 
@@ -25,7 +50,7 @@ Variable | Type | Description
 -------- | ---- | -----------
 `BATCH`   | integer  | Specifies the size of the batch. Defaults to 200.
 
-** Omnibus Installation**
+**Omnibus Installation**
 
 ```bash
 # gitlab-rake gitlab:uploads:migrate[uploader_class, model_class, mount_point]
@@ -40,6 +65,9 @@ gitlab-rake "gitlab:uploads:migrate[AttachmentUploader, Note, :attachment]"
 gitlab-rake "gitlab:uploads:migrate[AttachmentUploader, Appearance, :logo]"
 gitlab-rake "gitlab:uploads:migrate[AttachmentUploader, Appearance, :header_logo]"
 
+# Favicon
+gitlab-rake "gitlab:uploads:migrate[FaviconUploader, Appearance, :favicon]"
+
 # Markdown
 gitlab-rake "gitlab:uploads:migrate[FileUploader, Project]"
 gitlab-rake "gitlab:uploads:migrate[PersonalFileUploader, Snippet]"
@@ -65,6 +93,9 @@ sudo -u git -H bundle exec rake "gitlab:uploads:migrate[AttachmentUploader, Note
 sudo -u git -H bundle exec rake "gitlab:uploads:migrate[AttachmentUploader, Appearance, :logo]"
 sudo -u git -H bundle exec rake "gitlab:uploads:migrate[AttachmentUploader, Appearance, :header_logo]"
 
+# Favicon
+sudo -u git -H bundle exec rake "gitlab:uploads:migrate[FaviconUploader, Appearance, :favicon]"
+
 # Markdown
 sudo -u git -H bundle exec rake "gitlab:uploads:migrate[FileUploader, Project]"
 sudo -u git -H bundle exec rake "gitlab:uploads:migrate[PersonalFileUploader, Snippet]"

doc/development/file_storage.md

@@ -45,6 +45,11 @@ In the case of Issues/MR/Notes Markdown attachments, there is a different approa
 instead of basing the path into a mutable variable `:project_path_with_namespace`, it's possible to use the
 hash of the project ID instead, if project migrates to the new approach (introduced in 10.2).
 
+> Note: We provide an [all-in-one rake task] to migrate all uploads to object
+> storage in one go. If a new Uploader class or model type is introduced, make
+> sure you add a rake task invocation corresponding to it to the [category
+> list].
+
 ### Path segments
 
 Files are stored at multiple locations and use different path schemes. 
@@ -137,3 +142,5 @@ end
 
 [CarrierWave]: https://github.com/carrierwaveuploader/carrierwave
 [Hashed Storage]: ../administration/repository_storage_types.md
+[all-in-one rake task]: ../administration/raketasks/uploads/migrate.md
+[category list]: ../../lib/tasks/gitlab/uploads/migrate.rake#L6-16