Add documentation for Inline Diff

Signed-off-by: Rémy Coutable <remy@rymai.me>

CHANGELOG

@@ -6,6 +6,8 @@ v 8.8.0 (unreleased)
   - Assign labels and milestone to target project when moving issue. !3934 (Long Nguyen)
   - Use a case-insensitive comparison in sanitizing URI schemes
   - Toggle sign-up confirmation emails in application settings
+  - Added `InlineDiffFilter` to the markdown parser. (Adam Butler)
+  - Added inline diff styling for `change_title` system notes. (Adam Butler)
   - Project#open_branches has been cleaned up and no longer loads entire records into memory.
   - Escape HTML in commit titles in system note messages
   - Improve multiple branch push performance by memoizing permission checking
@@ -100,10 +102,6 @@ v 8.7.1
   - Prevent users from deleting Webhooks via API they do not own
   - Fix Error 500 due to stale cache when projects are renamed or transferred
   - Update width of search box to fix Safari bug. !3900 (Jedidiah)
-  - Added inline diff styling for `change_title` system notes. !3576 (Adam Butler)
-  - Added `InlineDiffFilter` to the markdown parser. !3576 (Adam Butler)
-
-v 8.7.1 (unreleased)
   - Use the `can?` helper instead of `current_user.can?`
 
 v 8.7.0

doc/markdown/markdown.md

@@ -8,6 +8,7 @@
 * [Multiple underscores in words](#multiple-underscores-in-words)
 * [URL auto-linking](#url-auto-linking)
 * [Code and Syntax Highlighting](#code-and-syntax-highlighting)
+* [Inline Diff](#inline-diff)
 * [Emoji](#emoji)
 * [Special GitLab references](#special-gitlab-references)
 * [Task lists](#task-lists)
@@ -153,6 +154,19 @@ s = "There is no highlighting for this."
 But let's throw in a <b>tag</b>.
 ```
 
+## Inline Diff
+
+With inline diffs tags you can display {+ additions +} or [- deletions -].
+
+The wrapping tags can be either curly braces or square brackets [+ additions +] or {- deletions -}.
+
+However the wrapping tags cannot be mixed as such:
+
+- {+ additions +]
+- [+ additions +}
+- {- deletions -]
+- [- deletions -}
+
 ## Emoji
 
 	Sometimes you want to :monkey: around a bit and add some :star2: to your :speech_balloon:. Well we have a gift for you: