Support XDG Base Directory Specification

Respect XDG_CONFIG_HOME and XDG_CONFIG_DIRS.
https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html#variables

Fixes #1048, closes #1061

features/authentication.feature

@@ -171,6 +171,57 @@ Feature: OAuth authentication
     Then the output should not contain "github.com password for mislav"
     And the file "../home/.config/hub" should contain "oauth_token: OTOKEN"
 
+  Scenario: XDG: legacy config found, credentials from GITHUB_USER & GITHUB_PASSWORD
+    Given I am "mislav" on github.com with OAuth token "LTOKEN"
+    And the GitHub API server:
+      """
+      post('/authorizations') {
+        assert_basic_auth 'mislav', 'kitty'
+        status 201
+        json :token => 'OTOKEN'
+      }
+      get('/user') {
+        json :login => 'mislav'
+      }
+      post('/user/repos') {
+        halt 401 unless request.env['HTTP_AUTHORIZATION'] == 'token OTOKEN'
+        status 201
+        json :full_name => 'mislav/dotfiles'
+      }
+      """
+    And $GITHUB_USER is "mislav"
+    And $GITHUB_PASSWORD is "kitty"
+    And $XDG_CONFIG_HOME is "$HOME/.xdg"
+    When I successfully run `hub create`
+    Then the file "../home/.xdg/hub" should contain "oauth_token: OTOKEN"
+    And the stderr should contain exactly:
+      """
+      Notice: config file found but not respected at: $HOME/.config/hub
+      You might want to move it to `$HOME/.xdg/hub' to avoid re-authenticating.\n
+      """
+
+  Scenario: XDG: config from secondary directories
+    Given I am "mislav" on github.com with OAuth token "OTOKEN"
+    And the GitHub API server:
+      """
+      get('/user') {
+        json :login => 'mislav'
+      }
+      post('/user/repos') {
+        halt 401 unless request.env['HTTP_AUTHORIZATION'] == 'token OTOKEN'
+        status 201
+        json :full_name => 'mislav/dotfiles'
+      }
+      """
+    And $GITHUB_USER is "mislav"
+    And $GITHUB_PASSWORD is "kitty"
+    And $XDG_CONFIG_HOME is "$HOME/.xdg"
+    And $XDG_CONFIG_DIRS is "/etc/xdg-nonsense:$HOME/.xdg-dir"
+    When I move the file named "../home/.config/hub" to "../home/.xdg-dir/hub"
+    And I successfully run `hub create`
+    Then the file "../home/.xdg/hub" should not exist
+    And the stderr should contain exactly ""
+
   Scenario: Credentials from GITHUB_TOKEN
     Given the GitHub API server:
       """
@@ -390,7 +441,7 @@ Feature: OAuth authentication
       When I run `hub create` interactively
       Then the output should contain:
         """
-        /home/.config/hub: permission denied\n
+        $HOME/.config/hub: permission denied\n
         """
       And the exit status should be 1
       And the file "../home/.config/hub" should not exist

features/steps.rb

@@ -40,7 +40,7 @@ Given(/^I am "([^"]*)" on ([\S]+)(?: with OAuth token "([^"]*)")?$/) do |name, h
 end
 
 Given(/^\$(\w+) is "([^"]*)"$/) do |name, value|
-  set_env name, value
+  set_env name, value.gsub(/\$([A-Z_]+)/) { ENV.fetch($1) }
 end
 
 Given(/^I am in "([^"]*)" git repo$/) do |dir_name|
@@ -153,6 +153,13 @@ Given(/^the current dir is not a repo$/) do
   end
 end
 
+When(/^I move the file named "([^"]+)" to "([^"]+)"?$/) do |source, dest|
+  in_current_dir do
+    FileUtils.mkdir_p(File.dirname(dest))
+    FileUtils.mv(source, dest)
+  end
+end
+
 Given(/^the GitHub API server:$/) do |endpoints_str|
   @server = Hub::LocalServer.start_sinatra do
     eval endpoints_str, binding

features/support/env.rb

@@ -191,4 +191,16 @@ World Module.new {
   def shell_escape(message)
     message.to_s.gsub(/['"\\ $]/) { |m| "\\#{m}" }
   end
+
+  %w[output_from stdout_from stderr_from all_stdout all_stderr].each do |m|
+    define_method(m) do |*args|
+      home = ENV['HOME'].to_s
+      output = super(*args)
+      if home.empty?
+        output
+      else
+        output.gsub(home, '$HOME')
+      end
+    end
+  end
 }

github/config.go

@@ -17,15 +17,6 @@ import (
 	"golang.org/x/crypto/ssh/terminal"
 )
 
-var defaultConfigsFile string
-
-func init() {
-	homeDir, err := homedir.Dir()
-	utils.Check(err)
-
-	defaultConfigsFile = filepath.Join(homeDir, ".config", "hub")
-}
-
 type yamlHost struct {
 	User       string `yaml:"user"`
 	OAuthToken string `yaml:"oauth_token"`
@@ -243,13 +234,65 @@ func (c *Config) selectHost() *Host {
 	return c.Hosts[i-1]
 }
 
+var defaultConfigsFile string
+
 func configsFile() string {
-	configsFile := os.Getenv("HUB_CONFIG")
-	if configsFile == "" {
-		configsFile = defaultConfigsFile
+	if configFromEnv := os.Getenv("HUB_CONFIG"); configFromEnv != "" {
+		return configFromEnv
+	}
+	if defaultConfigsFile == "" {
+		var err error
+		defaultConfigsFile, err = determineConfigLocation()
+		utils.Check(err)
+	}
+	return defaultConfigsFile
+}
+
+func homeConfig() (string, error) {
+	if home, err := homedir.Dir(); err != nil {
+		return "", err
+	} else {
+		return filepath.Join(home, ".config"), nil
+	}
+}
+
+func determineConfigLocation() (string, error) {
+	var err error
+
+	xdgHome := os.Getenv("XDG_CONFIG_HOME")
+	configDir := xdgHome
+	if configDir == "" {
+		if configDir, err = homeConfig(); err != nil {
+			return "", err
+		}
 	}
 
-	return configsFile
+	xdgDirs := os.Getenv("XDG_CONFIG_DIRS")
+	if xdgDirs == "" {
+		xdgDirs = "/etc/xdg"
+	}
+	searchDirs := append([]string{configDir}, strings.Split(xdgDirs, ":")...)
+
+	for _, dir := range searchDirs {
+		filename := filepath.Join(dir, "hub")
+		if _, err := os.Stat(filename); err == nil {
+			return filename, nil
+		}
+	}
+
+	configFile := filepath.Join(configDir, "hub")
+
+	if configDir == xdgHome {
+		if homeDir, _ := homeConfig(); homeDir != "" {
+			legacyConfig := filepath.Join(homeDir, "hub")
+			if _, err = os.Stat(legacyConfig); err == nil {
+				ui.Errorf("Notice: config file found but not respected at: %s\n", legacyConfig)
+				ui.Errorf("You might want to move it to `%s' to avoid re-authenticating.\n", configFile)
+			}
+		}
+	}
+
+	return configFile, nil
 }
 
 var currentConfig *Config
@@ -315,7 +358,7 @@ func CheckWriteable(filename string) error {
 // Public for testing purpose
 func CreateTestConfigs(user, token string) *Config {
 	f, _ := ioutil.TempFile("", "test-config")
-	defaultConfigsFile = f.Name()
+	os.Setenv("HUB_CONFIG", f.Name())
 
 	host := &Host{
 		User:        "jingweno",