add 3.1.2 TiDB release notes

TOC.md

@@ -427,6 +427,7 @@
     - [4.0.0-beta.1](/releases/release-4.0.0-beta.1.md)
     - [4.0.0-beta](/releases/release-4.0.0-beta.md)
   + v3.1
+    - [3.1.2](/releases/release-3.1.2.md)
     - [3.1.1](/releases/release-3.1.1.md)
     - [3.1.0 GA](/releases/release-3.1.0-ga.md)
     - [3.1.0-rc](/releases/release-3.1.0-rc.md)

releases/release-3.0.13.md

@@ -10,8 +10,6 @@ Release date: April 22, 2020
 
 TiDB version: 3.0.13
 
-TiUP version: 3.0.13
-
 ## Bug Fixes
 
 + TiDB

releases/release-3.0.14.md

@@ -10,8 +10,6 @@ Release date: May 9, 2020
 
 TiDB version: 3.0.14
 
-TiUP version: 3.0.14
-
 ## Compatibility Changes
 
 + TiDB

releases/release-3.1.2.md

@@ -0,0 +1,27 @@
+---
+title: TiDB 3.1.2 Release Notes
+category: Releases
+---
+
+# TiDB 3.1.2 Release Notes
+
+Release date: June 4, 2020
+
+TiDB version: 3.1.2
+
+## Bug Fixes
+
++ TiKV
+
+    - Fix the error handling issue during backup and restoration with S3 and GCS [#7965](https://github.com/tikv/tikv/pull/7965)
+    - Fix the `DefaultNotFound` error that occurs during restoration [#7838](https://github.com/tikv/tikv/pull/7938)
+
++ Tools
+
+    - Backup & Restore (BR)
+
+        - Retry automatically when the network is poor to improve stability with S3 and GCS storages [#314](https://github.com/pingcap/br/pull/314) [#7965](https://github.com/tikv/tikv/pull/7965)
+        - Fix a restoration failure that occurs because the Region leader cannot be found when restoring small tables [#303](https://github.com/pingcap/br/pull/303)
+        - Fix a data loss issue during restoration when a table’s row ID exceeds `2^(63)` [#323](https://github.com/pingcap/br/pull/323)
+        - Fix the issue that empty databases and tables cannot be restored [#318](https://github.com/pingcap/br/pull/318)
+        - Support using AWS KMS for server-side encryption (SSE) when targeting the S3 storage [#261](https://github.com/pingcap/br/pull/261)

releases/release-4.0.0-rc.1.md

@@ -10,8 +10,6 @@ Release date: April 28, 2020
 
 TiDB version: 4.0.0-rc.1
 
-TiUP version: 4.0.0-rc.1
-
 ## Compatibility Changes
 
 + TiKV

releases/release-4.0.0-rc.2.md

@@ -9,8 +9,6 @@ Release date: May 15, 2020
 
 TiDB version: 4.0.0-rc.2
 
-TiUP version: 4.0.0-rc.2
-
 ## Compatibility Changes
 
 + TiDB

releases/release-notes.md

@@ -17,6 +17,7 @@ aliases: ['/docs/dev/releases/rn/']
 
 ## 3.1
 
+- [3.1.2](/releases/release-3.1.2.md)
 - [3.1.1](/releases/release-3.1.1.md)
 - [3.1.0 GA](/releases/release-3.1.0-ga.md)
 - [3.1.0-rc](/releases/release-3.1.0-rc.md)