fix: Connect using DB_DSN env var

The DSN formation scheme is too rigid. There are so many possible
connection parameters, that supporting them all is just infeasible. It's
better to use the same piece of data for connecting to the DB in the
first place, that is the data source name. The standard library already
works this way and it should be a little easier to use godfish now that
there are fewer environment variables to manage.

README.md

@@ -42,15 +42,9 @@ set, then it checks the configuration file.
 
 #### connecting to the db
 
-Database connection parameters are always read from environment variables. The
-ones to set are:
-
+Database connection parameters are always read from environment variables. Set:
 ```
-DB_HOST=
-DB_NAME=
-DB_PASSWORD=
-DB_PORT=
-DB_USER=
+DB_DSN=
 ```
 
 #### configure file paths

driver.go

@@ -51,6 +51,8 @@ func NewDriver(dsn DSN, migConf *MigrationsConf) (driver Driver, err error) {
 // output will be passed to the standard library's sql.Open method.
 type DSN interface {
 	// Boot takes inputs from the host environment so it can create a Driver.
+	//
+	// Deprecated: Set the DB_DSN environment variable instead of using this.
 	Boot(ConnectionParams) error
 	// NewDriver calls the constructor of the corresponding Driver.
 	NewDriver(*MigrationsConf) (Driver, error)
@@ -59,6 +61,8 @@ type DSN interface {
 }
 
 // ConnectionParams is what to use when initializing a DSN.
+//
+// Deprecated: Set the DB_DSN environment variable instead of using this.
 type ConnectionParams struct {
 	Encoding string // Encoding is the client encoding for the connection.
 	Host     string // Host is the name of the host to connect to.

drivers/mysql/mysql.go

@@ -3,6 +3,7 @@ package mysql
 import (
 	"database/sql"
 	"fmt"
+	"os"
 	"os/exec"
 	"regexp"
 	"strings"
@@ -32,10 +33,7 @@ func (p *DSN) NewDriver(migConf *godfish.MigrationsConf) (godfish.Driver, error)
 
 // String generates a data source name (or connection URL) based on the fields.
 func (p *DSN) String() string {
-	return fmt.Sprintf(
-		"%s:%s@tcp(%s:%s)/%s",
-		p.User, p.Pass, p.Host, p.Port, p.Name,
-	)
+	return os.Getenv("DB_DSN")
 }
 
 // driver implements the godfish.Driver interface for mysql databases.

drivers/postgres/postgres.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"database/sql"
 	"fmt"
+	"os"
 	"os/exec"
 
 	"github.com/lib/pq"
@@ -31,10 +32,7 @@ func (p *DSN) NewDriver(migConf *godfish.MigrationsConf) (godfish.Driver, error)
 
 // String generates a data source name (or connection URL) based on the fields.
 func (p *DSN) String() string {
-	return fmt.Sprintf(
-		"postgresql://%s:%s/%s?client_encoding=%s&sslmode=require",
-		p.Host, p.Port, p.Name, p.Encoding,
-	)
+	return os.Getenv("DB_DSN")
 }
 
 // driver implements the Driver interface for postgres databases.

internal/commands/commands.go

@@ -76,12 +76,8 @@ Description:
 	Configuration options are set with flags or with a configuration file. Options
 	specified via flags will take precedence over the config file.
 
-	Specify database connection params with environment variables:
-		DB_HOST=
-		DB_NAME=
-		DB_PASSWORD=
-		DB_PORT=
-		DB_USER=
+	Specify database connection params with environment variable:
+		DB_DSN=
 
 	The following flags should go before the command.`,
 			bin)