Allow overriding config with flag and honor that during setup

Before this change the behavior was _always_ generate config at the
default path. This was to avoid confusion if you ran the command with
the flag one time and then not the next you would end up with more
than one config.

I think this behavior is least surprising that we would generate the
config at the given path if it didn't already exist.

config/config.go

@@ -3,6 +3,7 @@ package config
 import (
 	"fmt"
 	"os"
+	"path/filepath"
 
 	"github.com/spf13/viper"
 )
@@ -26,31 +27,26 @@ func (c *Config) Init() error {
 		return err
 	}
 
-	c.File = c.defaultFile()
-
 	// reload after creating config
 	err := c.read()
 	return err
 }
 
-// read tries to load the config either from Config.defaultPath or Config.file.
+// read tries to load the config either from (*Config).defaultPath() or (*Config).File.
 func (c *Config) read() error {
-	if c.File != "" {
-		viper.SetConfigFile(c.File)
-	}
-
-	if viper.ConfigFileUsed() == "" {
-		viper.AddConfigPath("$HOME/.circleci")
-		viper.SetConfigName(c.Name)
+	file, err := c.flagOrDefaultFile()
+	if err != nil {
+		return err
 	}
+	viper.SetConfigFile(file)
 
 	// read in environment variables that match
 	// set a prefix for config, i.e. CIRCLECI_CLI_ENDPOINT
 	viper.SetEnvPrefix("circleci_cli")
 	viper.AutomaticEnv()
 
 	// If a config file is found, read it in.
-	err := viper.ReadInConfig()
+	err = viper.ReadInConfig()
 	return err
 }
 
@@ -64,31 +60,63 @@ func (c *Config) defaultFile() string {
 	return fmt.Sprintf("%s/%s.yml", c.defaultPath(), c.Name)
 }
 
-func (c *Config) setupDefaults() error {
-	if _, err := os.Stat(c.defaultPath()); os.IsNotExist(err) {
-		if err = os.Mkdir(c.defaultPath(), 0700); err != nil {
-			return fmt.Errorf("Error creating directory: '%s'", c.defaultPath())
+func (c *Config) configPath() (string, error) {
+	file, err := c.flagOrDefaultFile()
+	if err != nil {
+		return c.defaultFile(), err
+	}
+
+	return filepath.Abs(filepath.Dir(file))
+}
+
+func (c *Config) flagOrDefaultFile() (string, error) {
+	if c.File != "" {
+		absFile, err := filepath.Abs(c.File)
+		if err != nil {
+			return c.defaultFile(), err
+		}
+		return absFile, err
+	}
+
+	return c.defaultFile(), nil
+}
+
+func (c *Config) setup() error {
+	path, err := c.configPath()
+
+	if err != nil {
+		return err
+	}
+
+	if _, err = os.Stat(path); os.IsNotExist(err) {
+		if err = os.Mkdir(path, 0700); err != nil {
+			return fmt.Errorf("Error creating directory: '%s'", path)
 		}
 	}
 
-	// Create default config file
-	_, err := os.Create(c.defaultFile())
+	// Create config file
+	file, err := c.flagOrDefaultFile()
+	if err != nil {
+		return err
+	}
+	_, err = os.Create(file)
 	return err
 }
 
 // create will generate a new config, after asking the user for their token.
 func (c *Config) create() error {
-	// Don't support creating config at --config flag, only default
-	if c.File != "" {
-		fmt.Printf("Setting up default config at: %v\n", c.defaultFile())
+	cfg, err := c.flagOrDefaultFile()
+	if err != nil {
+		return err
 	}
+	fmt.Printf("Setting up default config at: %v\n", cfg)
 
-	if err := c.setupDefaults(); err != nil {
+	if err = c.setup(); err != nil {
 		return err
 	}
 
 	// open file with read & write
-	file, err := os.OpenFile(c.defaultFile(), os.O_RDWR, 0600)
+	file, err := os.OpenFile(cfg, os.O_RDWR, 0600)
 	if err != nil {
 		return err
 	}
@@ -119,7 +147,7 @@ func (c *Config) create() error {
 		return err
 	}
 
-	fmt.Printf("Your configuration has been created in `%v`.\n", c.defaultFile())
+	fmt.Printf("Your configuration has been created in `%v`.\n", cfg)
 	fmt.Println("It can edited manually for advanced settings.")
 	return err
 }