Add tag protection (#15629)

* Added tag protection in hook.

* Prevent UI tag creation if protected.

* Added settings page.

* Added tests.

* Added suggestions.

* Moved tests.

* Use individual errors.

* Removed unneeded methods.

* Switched delete selector.

* Changed method names.

* No reason to be unique.

* Allow editing of protected tags.

* Removed unique key from migration.

* Added docs page.

* Changed date.

* Respond with 404 to not found tags.

* Replaced glob with regex pattern.

* Added support for glob and regex pattern.

* Updated documentation.

* Changed white* to allow*.

* Fixed edit button link.

* Added cancel button.

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

docs/content/doc/advanced/protected-tags.en-us.md

@@ -0,0 +1,57 @@
+---
+date: "2021-05-14T00:00:00-00:00"
+title: "Protected tags"
+slug: "protected-tags"
+weight: 45
+toc: false
+draft: false
+menu:
+  sidebar:
+    parent: "advanced"
+    name: "Protected tags"
+    weight: 45
+    identifier: "protected-tags"
+---
+
+# Protected tags
+
+Protected tags allow control over who has permission to create or update git tags. Each rule allows you to match either an individual tag name, or use an appropriate pattern to control multiple tags at once. 
+
+**Table of Contents**
+
+{{< toc >}}
+
+## Setting up protected tags
+
+To protect a tag, you need to follow these steps:
+
+1. Go to the repository’s **Settings** > **Tags** page.
+1. Type a pattern to match a name. You can use a single name, a [glob pattern](https://pkg.go.dev/github.com/gobwas/glob#Compile) or a regular expression.
+1. Choose the allowed users and/or teams. If you leave these fields empty noone is allowed to create or modify this tag.
+1. Select **Save** to save the configuration.
+
+## Pattern protected tags
+
+The pattern uses [glob](https://pkg.go.dev/github.com/gobwas/glob#Compile) or regular expressions to match a tag name. For regular expressions you need to enclose the pattern in slashes.
+
+Examples:
+
+| Type  | Pattern Protected Tag    | Possible Matching Tags                  |
+| ----- | ------------------------ | --------------------------------------- |
+| Glob  | `v*`                     | `v`, `v-1`, `version2`                  |
+| Glob  | `v[0-9]`                 | `v0`, `v1` up to `v9`                   |
+| Glob  | `*-release`              | `2.1-release`, `final-release`          |
+| Glob  | `gitea`                  | only `gitea`                            |
+| Glob  | `*gitea*`                | `gitea`, `2.1-gitea`, `1_gitea-release` |
+| Glob  | `{v,rel}-*`              | `v-`, `v-1`, `v-final`, `rel-`, `rel-x` |
+| Glob  | `*`                      | matches all possible tag names          |
+| Regex | `/\Av/`                  | `v`, `v-1`, `version2`                  |
+| Regex | `/\Av[0-9]\z/`           | `v0`, `v1` up to `v9`                   |
+| Regex | `/\Av\d+\.\d+\.\d+\z/`   | `v1.0.17`, `v2.1.0`                     |
+| Regex | `/\Av\d+(\.\d+){0,2}\z/` | `v1`, `v2.1`, `v1.2.34`                 |
+| Regex | `/-release\z/`           | `2.1-release`, `final-release`          |
+| Regex | `/gitea/`                | `gitea`, `2.1-gitea`, `1_gitea-release` |
+| Regex | `/\Agitea\z/`            | only `gitea`                            |
+| Regex | `/^gitea$/`              | only `gitea`                            |
+| Regex | `/\A(v\|rel)-/`          | `v-`, `v-1`, `v-final`, `rel-`, `rel-x` |
+| Regex | `/.+/`                   | matches all possible tag names          |