Move 0.2->0.3 DB migration utility into source tree

Latest version made is somewhat more problematic to build
executables with dependencies without a proper module tree.

cmd/migrate-db-0.2/README.md

@@ -0,0 +1,9 @@
+# migrate-db-0.2
+
+Simple utility for migration of maddy 0.2 imapsql to
+0.3 format. This is not done automatically since this is
+a destructive migration and removes password field.
+
+See Tutorials / Upgrading from older maddy versions.
+
+**This utility will be removed on 0.4 release.**

cmd/migrate-db-0.2/migrate.go

@@ -0,0 +1,104 @@
+package main
+
+import (
+	"database/sql"
+	"fmt"
+	"os"
+	"time"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Printf("Usage: %s <DB file path>\n", os.Args[0])
+		return
+	}
+
+	fmt.Println("Seriously, take a DB backup now. I will give you 5 seconds to abort.")
+	time.Sleep(5 * time.Second)
+
+	/* In go-imap-sql used by maddy 0.2:
+	            id BIGSERIAL NOT NULL PRIMARY KEY AUTOINCREMENT,
+				username VARCHAR(255) NOT NULL UNIQUE,
+				msgsizelimit INTEGER DEFAULT NULL,
+				password VARCHAR(255) DEFAULT NULL,
+				password_salt VARCHAR(255) DEFAULT NULL,
+	            inboxId BIGINT DEFAULT 0
+	*/
+	/* In go-imap-sql used by maddy 0.3:
+				id BIGSERIAL NOT NULL PRIMARY KEY AUTOINCREMENT,
+				username VARCHAR(255) NOT NULL UNIQUE,
+				msgsizelimit INTEGER DEFAULT NULL,
+	            inboxId BIGINT DEFAULT 0
+	*/
+
+	db, err := sql.Open("sqlite3", os.Args[1])
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	defer db.Close()
+	if err := db.Ping(); err != nil {
+		fmt.Println(err)
+		return
+	}
+	db.SetMaxOpenConns(1)
+
+	fmt.Println("Disabling foreign keys...")
+	db.Exec("PRAGMA foreign_keys=OFF")
+
+	fmt.Println("Taking exclusive DB lock...")
+	db.Exec("PRAGMA locking_mode=EXCLUSIVE")
+	tx, err := db.Begin()
+	if err != nil {
+		fmt.Println("Tx begin:", err)
+		return
+	}
+	defer tx.Rollback()
+
+	fmt.Println("Creating new users table...")
+	_, err = tx.Exec(`
+        CREATE TABLE __new_users (
+            id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
+			username VARCHAR(255) NOT NULL UNIQUE,
+			msgsizelimit INTEGER DEFAULT NULL,
+            inboxId BIGINT DEFAULT 0
+        )`)
+	if err != nil {
+		fmt.Println("Create new table:", err)
+		return
+	}
+
+	fmt.Println("Moving data from old table...")
+	_, err = tx.Exec(`
+        INSERT INTO __new_users
+        SELECT id, username, msgsizelimit, inboxId
+        FROM users`)
+	if err != nil {
+		fmt.Println("Data move:", err)
+		return
+	}
+
+	fmt.Println("Removing old table...")
+	_, err = tx.Exec(`DROP TABLE users`)
+	if err != nil {
+		fmt.Println("Table drop:", err)
+		return
+	}
+
+	fmt.Println("Renaming new table to the normal name...")
+	_, err = tx.Exec(`ALTER TABLE __new_users RENAME TO users`)
+	if err != nil {
+		fmt.Println("Table rename:", err)
+		return
+	}
+
+	fmt.Println("Completing transaction...")
+	if err := tx.Commit(); err != nil {
+		fmt.Println("Tx commit:", err)
+		return
+	}
+
+	fmt.Println("Done! Now go back and run maddyctl to readd passwords to DB.")
+}

docs/tutorials/upgrading.md

@@ -20,8 +20,8 @@ be used in 0.3 and auto-migration is not possible. Additionally, the way
 passwords are hashed is changed, meaning that after migration passwords will
 need to be reset.
 
-**migrate.go script is SQLite-specific, if you need one that works for
-Postgres - reach out at IRC channel.**
+**Migration utility is SQLite-specific, if you need one that works for
+Postgres - reach out at the IRC channel.**
 
 1. Make sure the server is not running.
 
@@ -36,19 +36,21 @@ mkdir backup
 cp /var/lib/maddy/imapsql.db* backup/
 ```
 
-3. Download migrate.go from https://gist.github.com/foxcpp/1be0b627f9d2be6004c3867be186b7fb
-4. Compile it:
+3. Compile migration utility:
 
 ```
-env GO111MODULE=on go build migrate.go
+git clone https://github/foxcpp/maddy.git
+cd maddy/cmd/migrate-db-0.2
+go build
 ```
 
-5. Run compiled binary:
+4. Run compiled binary:
 
 ```
-./migrate /var/lib/maddy/imapsql.db
+./migrate-db-0.2 /var/lib/maddy/imapsql.db
 ```
-6. Open maddy.conf and make following changes:
+
+5. Open maddy.conf and make following changes:
 
 Remove `local_authdb` name from imapsql configuration block:
 ```
@@ -70,10 +72,10 @@ pass_table local_authdb {
 }
 ```
 
-7. Use `maddyctl creds create ACCOUNT_NAME` to add credentials to `pass_table`
+6. Use `maddyctl creds create ACCOUNT_NAME` to add credentials to `pass_table`
    store.
 
-8. Start the server back.
+7. Start the server back.
 
 ```
 systemctl start maddy