Fix broken links and other minor improvements

doc/install/database_mysql.md

 # Database MySQL
 
-> **Note:**
-> - We do not recommend using MySQL due to various issues. For example, case
-    [(in)sensitivity](https://dev.mysql.com/doc/refman/5.0/en/case-sensitivity.html)
-    and [problems](https://bugs.mysql.com/bug.php?id=65830) that
-    [suggested](https://bugs.mysql.com/bug.php?id=50909)
-    [fixes](https://bugs.mysql.com/bug.php?id=65830) [have](https://bugs.mysql.com/bug.php?id=63164).
+NOTE: **Note:**
+We do not recommend using MySQL due to various issues.
+For example, there have been bugs with case
+[(in)sensitivity](https://dev.mysql.com/doc/refman/5.7/en/case-sensitivity.html).
+
+Bugs relating to case sensitivity:
+
+- <https://bugs.mysql.com/bug.php?id=65830>
+- <https://bugs.mysql.com/bug.php?id=50909>
+- <https://bugs.mysql.com/bug.php?id=65830>
+- <https://bugs.mysql.com/bug.php?id=63164>
 
 ## Initial database setup
 
-```
+```sh
 # Install the database packages
 sudo apt-get install -y mysql-server mysql-client libmysqlclient-dev
 
@@ -84,8 +89,9 @@ GitLab 8.14 has introduced [a feature](https://gitlab.com/gitlab-org/gitlab-ce/m
 Follow the below instructions to ensure you use the most up to date requirements for your GitLab MySQL Database.
 
 **We are about to do the following:**
+
 - Ensure you can enable `utf8mb4` encoding and `utf8mb4_general_ci` collation for your GitLab DB, tables and data.
-- Convert your GitLab tables and data from `utf8`/`utf8_general_ci` to `utf8mb4`/`utf8mb4_general_ci`
+- Convert your GitLab tables and data from `utf8`/`utf8_general_ci` to `utf8mb4`/`utf8mb4_general_ci`.
 
 ### Check for utf8mb4 support
 
@@ -130,7 +136,8 @@ We need to check, enable and maybe convert your existing GitLab DB tables to the
 
 Whatever the results of your checks above, we now need to check if your GitLab database has been created using [InnoDB File-Per-Table Tablespaces](http://dev.mysql.com/doc/refman/5.7/en/innodb-multiple-tablespaces.html) (i.e. `innodb_file_per_table` was set to **1** at initial setup time).
 
-> Note: This setting is [enabled by default](http://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_file_per_table) since MySQL 5.6.6.
+NOTE: **Note:**
+This setting is [enabled by default](http://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_file_per_table) since MySQL 5.6.6.
 
     # Run this command with root privileges, replace the data dir if different:
     sudo ls -lh /var/lib/mysql/gitlabhq_production/*.ibd | wc -l
@@ -138,20 +145,19 @@ Whatever the results of your checks above, we now need to check if your GitLab d
     # Run this command with root privileges, replace the data dir if different:
     sudo ls -lh /var/lib/mysql/gitlabhq_production/*.frm | wc -l
 
-
 - **Case 1: a result > 0 for both commands**
 
-Congrats, your GitLab database uses the right InnoDB tablespace format.
+Congratulations, your GitLab database uses the right InnoDB tablespace format.
 
 However, you must still ensure that any **future tables** created by GitLab will still use the right format:
 
 - If `SELECT @@innodb_file_per_table` returned **1** previously, your server is running correctly.
 
-    > It's however a requirement to check *now* that this setting is indeed persisted in your [my.cnf](https://dev.mysql.com/doc/refman/5.7/en/tablespace-enabling.html) file!
+    > It's however a requirement to check *now* that this setting is indeed persisted in your [`my.cnf`](https://dev.mysql.com/doc/refman/5.7/en/innodb-multiple-tablespaces.html) file!
 
 - If `SELECT @@innodb_file_per_table` returned **0** previously, your server is not running correctly.
 
-    > [Enable innodb_file_per_table](https://dev.mysql.com/doc/refman/5.7/en/tablespace-enabling.html) by running in a MySQL session as root the command `SET GLOBAL innodb_file_per_table=1, innodb_file_format=Barracuda;` and persist the two settings in your [my.cnf](https://dev.mysql.com/doc/refman/5.7/en/tablespace-enabling.html) file
+    > [Enable innodb_file_per_table](https://dev.mysql.com/doc/refman/5.7/en/innodb-multiple-tablespaces.html) by running in a MySQL session as root the command `SET GLOBAL innodb_file_per_table=1, innodb_file_format=Barracuda;` and persist the two settings in your [`my.cnf`](https://dev.mysql.com/doc/refman/5.7/en/innodb-multiple-tablespaces.html) file.
 
 Now, if you have a **different result** returned by the 2 commands above, it means you have a **mix of tables format** uses in your GitLab database. This can happen if your MySQL server had different values for `innodb_file_per_table` in its life and you updated GitLab at different moments with those inconsistent values. So keep reading.
 
@@ -172,7 +178,7 @@ Let's enable what we need on the running server:
     # You can now quit the database session
     mysql> \q
 
-> Now, **persist** [innodb_file_per_table](https://dev.mysql.com/doc/refman/5.6/en/tablespace-enabling.html) and [innodb_file_format](https://dev.mysql.com/doc/refman/5.6/en/innodb-file-format-enabling.html) in your `my.cnf` file.
+> Now, **persist** [innodb_file_per_table](https://dev.mysql.com/doc/refman/5.7/en/innodb-multiple-tablespaces.html) and [innodb_file_format](https://dev.mysql.com/doc/refman/5.7/en/innodb-file-format-enabling.html) in your `my.cnf` file.
 
 Ensure at this stage that your GitLab instance is indeed **stopped**.
 
@@ -184,7 +190,7 @@ Now, let's convert all the GitLab database tables to the new tablespace format:
     # Type the MySQL root password
     mysql > use gitlabhq_production;
 
-    # Safety check: you should still have those values set as follow:
+    # Safety check: you should still have those values set as follows:
     mysql> SELECT @@innodb_file_per_table, @@innodb_file_format;
     +-------------------------+----------------------+
     | @@innodb_file_per_table | @@innodb_file_format |
@@ -203,7 +209,7 @@ Now, let's convert all the GitLab database tables to the new tablespace format:
 
 #### Check for proper InnoDB File Format, Row Format, Large Prefix and tables conversion
 
-We need to check, enable and probably convert your existing GitLab DB tables to use the [Barracuda InnoDB file format](https://dev.mysql.com/doc/refman/5.6/en/innodb-file-format.html), the [DYNAMIC row format](https://dev.mysql.com/doc/refman/5.6/en/glossary.html#glos_dynamic_row_format) and [innodb_large_prefix](http://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_large_prefix) as a second prerequisite for supporting **utfb8mb4 with long indexes** used by recent GitLab databases.
+We need to check, enable and probably convert your existing GitLab DB tables to use the [Barracuda InnoDB file format](https://dev.mysql.com/doc/refman/5.7/en/innodb-file-format.html), the [DYNAMIC row format](https://dev.mysql.com/doc/refman/5.7/en/glossary.html#glos_dynamic_row_format) and [innodb_large_prefix](http://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_large_prefix) as a second prerequisite for supporting **utfb8mb4 with long indexes** used by recent GitLab databases.
 
     # Login to MySQL
     mysql -u root -p
@@ -229,7 +235,7 @@ We need to check, enable and probably convert your existing GitLab DB tables to
     | utf8                     | utf8_general_ci      |
     +--------------------------+----------------------+
 
-> Now, ensure that [innodb_file_format](https://dev.mysql.com/doc/refman/5.6/en/tablespace-enabling.html) and [innodb_large_prefix](http://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_large_prefix) are **persisted** in your `my.cnf` file.
+> Now, ensure that [innodb_file_format](https://dev.mysql.com/doc/refman/5.7/en/innodb-multiple-tablespaces.html) and [innodb_large_prefix](http://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_large_prefix) are **persisted** in your `my.cnf` file.
 
 #### Tables and data conversion to utf8mb4
 
@@ -257,7 +263,7 @@ Now that you have a persistent MySQL setup, you can safely upgrade tables after
 
 Ensure your GitLab database configuration file uses a proper connection encoding and collation:
 
-```sudo -u git -H editor config/database.yml```
+`sudo -u git -H editor config/database.yml`
 
     production:
       adapter: mysql2
@@ -266,19 +272,19 @@ Ensure your GitLab database configuration file uses a proper connection encoding
 
 [Restart your GitLab instance](../administration/restart_gitlab.md).
 
-
 ## MySQL strings limits
 
 After installation or upgrade, remember to run the `add_limits_mysql` Rake task:
 
 **Omnibus GitLab installations**
-```
+
+```sh
 sudo gitlab-rake add_limits_mysql
 ```
 
 **Installations from source**
 
-```
+```sh
 bundle exec rake add_limits_mysql RAILS_ENV=production
 ```