Add code block declarations

Declare languages for code blocks.

doc/security/rack_attack.md

@@ -60,7 +60,7 @@ default['gitlab']['gitlab-rails']['rack_attack_protected_paths'] = [
 
 This header is included in responses to blocked requests:
 
-```
+```plaintext
 Retry-After: 60
 ```
 
@@ -109,7 +109,7 @@ No response headers are provided.
 
 1. Reconfigure GitLab:
 
-   ```
+   ```shell
    sudo gitlab-ctl reconfigure
    ```
 
@@ -202,7 +202,7 @@ the load balancer. In that case, you will need to:
 1. Whitelist the load balancer's IP address(es) in the Rack Attack [settings](#settings).
 1. Reconfigure GitLab:
 
-   ```
+   ```shell
    sudo gitlab-ctl reconfigure
    ```
 

doc/ssh/README.md

@@ -124,7 +124,7 @@ To create a new SSH key pair:
    If, in any case, you want to add or change the password of your SSH key pair,
    you can use the `-p` flag:
 
-   ```
+   ```shell
    ssh-keygen -p -f <keyname>
    ```
 
@@ -206,7 +206,7 @@ authenticity of the GitLab host you are connecting to.
 For example, when connecting to GitLab.com, answer `yes` to add GitLab.com to
 the list of trusted hosts:
 
-```
+```plaintext
 The authenticity of host 'gitlab.com (35.231.145.151)' can't be established.
 ECDSA key fingerprint is SHA256:HbW3g8zUjNSksFbqTiUWPWg2Bq1x8xdGUrliXFzSnUw.
 Are you sure you want to continue connecting (yes/no)? yes
@@ -423,8 +423,9 @@ security risks.
 The GitLab check process includes a check for this condition, and will direct you
 to this section if your server is configured like this, e.g.:
 
-```
+```shell
 $ gitlab-rake gitlab:check
+
 # ...
 Git user has default SSH configuration? ... no
   Try fixing it:

doc/system_hooks/system_hooks.md

@@ -41,7 +41,7 @@ for Push and Tag events, but we never display commits.
 
 **Request header**:
 
-```
+```plaintext
 X-Gitlab-Event: System Hook
 ```
 
@@ -396,7 +396,7 @@ It generates one event per modified branch.
 
 **Request header**:
 
-```
+```plaintext
 X-Gitlab-Event: System Hook
 ```
 
@@ -462,7 +462,7 @@ It generates one event per modified tag.
 
 **Request header**:
 
-```
+```plaintext
 X-Gitlab-Event: System Hook
 ```
 
@@ -516,7 +516,7 @@ updated/merged/closed or a commit is added in the source branch.
 
 **Request header**:
 
-```
+```plaintext
 X-Gitlab-Event: System Hook
 ```
 
@@ -643,7 +643,7 @@ Triggered only once when you push to the repository (including tags).
 
 **Request header**:
 
-```
+```plaintext
 X-Gitlab-Event: System Hook
 ```
 

doc/update/mysql_to_postgresql.md

@@ -54,13 +54,13 @@ pgloader within the container as it is not included in the container image.
 
 1. Start a shell session in the context of the running container:
 
-   ``` bash
+   ```shell
    docker exec -it gitlab bash
    ```
 
 1. Install pgloader:
 
-   ``` bash
+   ```shell
    apt-get update
    apt-get -y install pgloader
    ```
@@ -78,7 +78,7 @@ need to enable the bundled PostgreSQL:
 
 1. Edit `/etc/gitlab/gitlab.rb` to enable bundled PostgreSQL:
 
-   ```
+   ```ruby
    postgresql['enable'] = true
    ```
 
@@ -116,7 +116,7 @@ new PostgreSQL one:
 1. Save the following snippet in a `commands.load` file, and edit with your
    MySQL database `username`, `password` and `host`:
 
-   ```
+   ```sql
    LOAD DATABASE
         FROM mysql://username:password@host/gitlabhq_production
         INTO postgresql://gitlab-psql@unix://var/opt/gitlab/postgresql:/gitlabhq_production
@@ -143,7 +143,7 @@ new PostgreSQL one:
 1. Once the migration finishes, you should see a summary table that looks like
    the following:
 
-   ```
+   ```plaintext
                                     table name       read   imported     errors      total time
    -----------------------------------------------  ---------  ---------  ---------  --------------
                                    fetch meta data        119        119          0          0.388s
@@ -217,7 +217,7 @@ new PostgreSQL one:
 1. Save the following snippet in a `commands.load` file, and edit with your
    MySQL `username`, `password` and `host`:
 
-   ```
+   ```sql
    LOAD DATABASE
         FROM mysql://username:password@host/gitlabhq_production
         INTO postgresql://postgres@unix://var/run/postgresql:/gitlabhq_production
@@ -244,7 +244,7 @@ new PostgreSQL one:
 1. Once the migration finishes, you should see a summary table that looks like
    the following:
 
-   ```
+   ```plaintext
                                     table name       read   imported     errors      total time
    -----------------------------------------------  ---------  ---------  ---------  --------------
                                    fetch meta data        119        119          0          0.388s
@@ -284,7 +284,7 @@ Sometimes, you might encounter some errors during or after the migration.
 The PostgreSQL user that you use for the migration MUST have **superuser** privileges.
 Otherwise, you may see a similar message to the following:
 
-```
+```plaintext
 debugger invoked on a CL-POSTGRES-ERROR:INSUFFICIENT-PRIVILEGE in thread
     #<THREAD "lparallel" RUNNING {10078A3513}>:
       Database error 42501: permission denied: "RI_ConstraintTrigger_a_20937" is a system trigger

doc/update/restore_after_failure.md

@@ -28,7 +28,7 @@ may need to manually correct the problem next time you upgrade.
 
 Example error:
 
-```
+```plaintext
 == 20151103134857 CreateLfsObjects: migrating =================================
 -- create_table(:lfs_objects)
 rake aborted!
@@ -48,7 +48,7 @@ need to do.
 Pass the version to a database rake task to manually mark the migration as
 complete.
 
-```
+```shell
 # Source install
 sudo -u git -H bundle exec rake gitlab:db:mark_migration_complete[20151103134857] RAILS_ENV=production
 
@@ -62,7 +62,7 @@ migrations are marked complete.
 
 ### GitLab < 8.6
 
-```
+```shell
 # Source install
 sudo -u git -H bundle exec rails console -e production
 
@@ -72,7 +72,7 @@ sudo gitlab-rails console
 
 At the Rails console, type the following commands:
 
-```
+```ruby
 ActiveRecord::Base.connection.execute("INSERT INTO schema_migrations (version) VALUES('20151103134857')")
 exit
 ```