fix: use READ COMMITTED transactions on MySQL and MariaDB (#39506)

MariaDB 11.6.2+ defaults `innodb_snapshot_isolation` to `ON`, which
fails REPEATABLE READ transactions with error 1020 when a row they write
changed after their first read. Gitea's background work like push
processing writes the same rows, so merges, issue closes and workflow
runs fail sporadically.

- Use READ COMMITTED on MySQL and MariaDB, like PostgreSQL and MSSQL
- Update xorm to v1.4.3

Replaces: https://github.com/go-gitea/gitea/pull/39494
Fixes: https://github.com/go-gitea/gitea/issues/39492

---------

Signed-off-by: silverwind <me@silverwind.io>

go.mod

@@ -109,7 +109,7 @@ require (
 	modernc.org/sqlite v1.59.0
 	mvdan.cc/xurls/v2 v2.6.0
 	xorm.io/builder v0.3.13
-	xorm.io/xorm v1.4.1
+	xorm.io/xorm v1.4.3
 )
 
 require (

go.sum

@@ -862,5 +862,5 @@ pgregory.net/rapid v0.4.2 h1:lsi9jhvZTYvzVpeG93WWgimPRmiJQfGFRNTEZh1dtY0=
 pgregory.net/rapid v0.4.2/go.mod h1:UYpPVyjFHzYBGHIxLFoupi8vwk6rXNzRY9OMvVxFIOU=
 xorm.io/builder v0.3.13 h1:a3jmiVVL19psGeXx8GIurTp7p0IIgqeDmwhcR6BAOAo=
 xorm.io/builder v0.3.13/go.mod h1:aUW0S9eb9VCaPohFCH3j7czOx1PMW3i1HrSzbLYGBSE=
-xorm.io/xorm v1.4.1 h1:m7QlNd0eBGb31IV4Q/ow0Du83rtdC1CiwlvJZGvYde8=
-xorm.io/xorm v1.4.1/go.mod h1:cs0ePc8O4a0jD78cNvD+0VFwhqotTvLQZv372QsDw7Q=
+xorm.io/xorm v1.4.3 h1:MwWFWzVr+/6D07qGCDhBAfABcuT0gvqY3XmTy1215BM=
+xorm.io/xorm v1.4.3/go.mod h1:cs0ePc8O4a0jD78cNvD+0VFwhqotTvLQZv372QsDw7Q=

models/db/engine_init.go

@@ -5,6 +5,7 @@ package db
 
 import (
 	"context"
+	"database/sql"
 	"fmt"
 
 	"gitea.dev/modules/log"
@@ -59,6 +60,11 @@ func InitEngine(ctx context.Context) error {
 	xe.SetMaxIdleConns(setting.Database.MaxIdleConns)
 	xe.SetConnMaxLifetime(setting.Database.ConnMaxLifetime)
 
+	if setting.Database.Type.IsMySQL() {
+		// like PostgreSQL and MSSQL, avoids MariaDB snapshot isolation errors
+		xe.SetDefaultTxOptions(&sql.TxOptions{Isolation: sql.LevelReadCommitted})
+	}
+
 	if setting.Database.SlowQueryThreshold > 0 {
 		xe.AddHook(&EngineHook{
 			Threshold: setting.Database.SlowQueryThreshold,