From 9974f3dadd5d8e6025c2a240049b85828313a2cc Mon Sep 17 00:00:00 2001
From: Quinten Palmer <quinten@clypd.com>
Date: Fri, 16 Nov 2018 13:33:22 -0500
Subject: [PATCH 1/3] Rename to GetConfigFromFile

This function reads the map of config environments to Environment
structs from the dbconfig.yml file. We want to allow these commands to
also read from the shell environment, so for unambiguous names this is
being renamed.
---
 sql-migrate/config.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sql-migrate/config.go b/sql-migrate/config.go
index 67906065..eb600c27 100644
--- a/sql-migrate/config.go
+++ b/sql-migrate/config.go
@@ -39,7 +39,7 @@ type Environment struct {
 	SchemaName string `yaml:"schema"`
 }
 
-func ReadConfig() (map[string]*Environment, error) {
+func ReadConfigFromFile() (map[string]*Environment, error) {
 	file, err := ioutil.ReadFile(ConfigFile)
 	if err != nil {
 		return nil, err
@@ -55,7 +55,7 @@ func ReadConfig() (map[string]*Environment, error) {
 }
 
 func GetEnvironment() (*Environment, error) {
-	config, err := ReadConfig()
+	config, err := ReadConfigFromFile()
 	if err != nil {
 		return nil, err
 	}

From 0c5f5e41d16a9a7c9ea602a0e187be3b4dadfc55 Mon Sep 17 00:00:00 2001
From: Quinten Palmer <quinten@clypd.com>
Date: Fri, 16 Nov 2018 13:39:32 -0500
Subject: [PATCH 2/3] ReadEnvFromFile now returns the env instead of a config

This is in the same vein of the previous commit where we want to be able
to parse an Environment from the shell environment, so to make that
switch easier, this function now returns the Environemnt and can be
substituted for another function which reads from the environment.
---
 sql-migrate/config.go | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/sql-migrate/config.go b/sql-migrate/config.go
index eb600c27..b32c307a 100644
--- a/sql-migrate/config.go
+++ b/sql-migrate/config.go
@@ -39,7 +39,7 @@ type Environment struct {
 	SchemaName string `yaml:"schema"`
 }
 
-func ReadConfigFromFile() (map[string]*Environment, error) {
+func ReadEnvFromFile() (*Environment, error) {
 	file, err := ioutil.ReadFile(ConfigFile)
 	if err != nil {
 		return nil, err
@@ -51,20 +51,20 @@ func ReadConfigFromFile() (map[string]*Environment, error) {
 		return nil, err
 	}
 
-	return config, nil
+	env := config[ConfigEnvironment]
+	if env == nil {
+		return nil, errors.New("No environment: " + ConfigEnvironment)
+	}
+
+	return env, nil
 }
 
 func GetEnvironment() (*Environment, error) {
-	config, err := ReadConfigFromFile()
+	env, err := ReadEnvFromFile()
 	if err != nil {
 		return nil, err
 	}
 
-	env := config[ConfigEnvironment]
-	if env == nil {
-		return nil, errors.New("No environment: " + ConfigEnvironment)
-	}
-
 	if env.Dialect == "" {
 		return nil, errors.New("No dialect specified")
 	}

From b0d42304b35b60443fe1428726e4c70bc610a5a3 Mon Sep 17 00:00:00 2001
From: Quinten Palmer <quinten@clypd.com>
Date: Fri, 16 Nov 2018 14:30:01 -0500
Subject: [PATCH 3/3] Fallback to reading Environment from shell Env

We want to build the ability for this command to accept the Environment
through the shell env. If the file is not present, we optimistically
look for the Environment in said shell env. There are existing
zero-value checks to make sure that a user doesn't accidentally end up
with no values for anything if their file was empty. We do a separate
stat to check for the file to keep the complexity of the fallback
simpler.

The envconfig package can be researched more here:

https://github.com/kelseyhightower/envconfig
---
 sql-migrate/config.go | 40 ++++++++++++++++++++++++++++++++--------
 1 file changed, 32 insertions(+), 8 deletions(-)

diff --git a/sql-migrate/config.go b/sql-migrate/config.go
index b32c307a..a845e4f8 100644
--- a/sql-migrate/config.go
+++ b/sql-migrate/config.go
@@ -8,6 +8,7 @@ import (
 	"io/ioutil"
 	"os"
 
+	"github.com/kelseyhightower/envconfig"
 	"github.com/rubenv/sql-migrate"
 	"gopkg.in/gorp.v1"
 	"gopkg.in/yaml.v2"
@@ -32,11 +33,24 @@ func ConfigFlags(f *flag.FlagSet) {
 }
 
 type Environment struct {
-	Dialect    string `yaml:"dialect"`
-	DataSource string `yaml:"datasource"`
-	Dir        string `yaml:"dir"`
-	TableName  string `yaml:"table"`
-	SchemaName string `yaml:"schema"`
+	Dialect    string `yaml:"dialect" envconfig:"DIALECT"`
+	DataSource string `yaml:"datasource" envconfig:"DATASOURCE"`
+	Dir        string `yaml:"dir" envconfig:"DIR"`
+	TableName  string `yaml:"table" envconfig:"TABLE"`
+	SchemaName string `yaml:"schema" envconfig:"SCHEMA"`
+}
+
+func ConfigPresent() bool {
+	_, err := os.Stat(ConfigFile)
+	return !os.IsNotExist(err)
+}
+
+func ReadEnv() (*Environment, error) {
+	env := &Environment{}
+	if err := envconfig.Process("", env); err != nil {
+		return nil, err
+	}
+	return env, nil
 }
 
 func ReadEnvFromFile() (*Environment, error) {
@@ -60,9 +74,19 @@ func ReadEnvFromFile() (*Environment, error) {
 }
 
 func GetEnvironment() (*Environment, error) {
-	env, err := ReadEnvFromFile()
-	if err != nil {
-		return nil, err
+	var env *Environment
+	if ConfigPresent() {
+		var err error
+		env, err = ReadEnvFromFile()
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		var err error
+		env, err = ReadEnv()
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	if env.Dialect == "" {