config: add UserSettings.ConfigFinder

Fixes #48.

config.go

@@ -53,6 +53,8 @@ type configFinder func() string
 // files are parsed and cached the first time Get() or GetStrict() is called.
 type UserSettings struct {
 	IgnoreErrors       bool
+	customConfig       *Config
+	customConfigFinder configFinder
 	systemConfig       *Config
 	systemConfigFinder configFinder
 	userConfig         *Config
@@ -203,6 +205,13 @@ func (u *UserSettings) GetStrict(alias, key string) (string, error) {
 	if u.onceErr != nil && u.IgnoreErrors == false {
 		return "", u.onceErr
 	}
+	// TODO this is getting repetitive
+	if u.customConfig != nil {
+		val, err := findVal(u.customConfig, alias, key)
+		if err != nil || val != "" {
+			return val, err
+		}
+	}
 	val, err := findVal(u.userConfig, alias, key)
 	if err != nil || val != "" {
 		return val, err
@@ -228,6 +237,12 @@ func (u *UserSettings) GetAllStrict(alias, key string) ([]string, error) {
 	if u.onceErr != nil && u.IgnoreErrors == false {
 		return nil, u.onceErr
 	}
+	if u.customConfig != nil {
+		val, err := findAll(u.customConfig, alias, key)
+		if err != nil || val != nil {
+			return val, err
+		}
+	}
 	val, err := findAll(u.userConfig, alias, key)
 	if err != nil || val != nil {
 		return val, err
@@ -243,16 +258,38 @@ func (u *UserSettings) GetAllStrict(alias, key string) ([]string, error) {
 	return []string{}, nil
 }
 
+// ConfigFinder will invoke f to try to find a ssh config file in a custom
+// location on disk, instead of in /etc/ssh or $HOME/.ssh. f should return the
+// name of a file containing SSH configuration.
+//
+// ConfigFinder must be invoked before any calls to Get or GetStrict and panics
+// if f is nil. Most users should not need to use this function.
+func (u *UserSettings) ConfigFinder(f func() string) {
+	if f == nil {
+		panic("cannot call ConfigFinder with nil function")
+	}
+	u.customConfigFinder = f
+}
+
 func (u *UserSettings) doLoadConfigs() {
 	u.loadConfigs.Do(func() {
-		// can't parse user file, that's ok.
 		var filename string
+		var err error
+		if u.customConfigFinder != nil {
+			filename = u.customConfigFinder()
+			u.customConfig, err = parseFile(filename)
+			// IsNotExist should be returned because a user specified this
+			// function - not existing likely means they made an error
+			if err != nil {
+				u.onceErr = err
+			}
+			return
+		}
 		if u.userConfigFinder == nil {
 			filename = userConfigFinder()
 		} else {
 			filename = u.userConfigFinder()
 		}
-		var err error
 		u.userConfig, err = parseFile(filename)
 		//lint:ignore S1002 I prefer it this way
 		if err != nil && os.IsNotExist(err) == false {

config_test.go

@@ -455,3 +455,15 @@ func TestNoTrailingNewline(t *testing.T) {
 		t.Errorf("wrong port: got %q want 4242", port)
 	}
 }
+
+func TestCustomFinder(t *testing.T) {
+	us := &UserSettings{}
+	us.ConfigFinder(func() string {
+		return "testdata/config1"
+	})
+
+	val := us.Get("wap", "User")
+	if val != "root" {
+		t.Errorf("expected to find User root, got %q", val)
+	}
+}

example_test.go

@@ -2,6 +2,7 @@ package ssh_config_test
 
 import (
 	"fmt"
+	"path/filepath"
 	"strings"
 
 	"github.com/kevinburke/ssh_config"
@@ -46,3 +47,12 @@ func ExampleDefault() {
 	// 22
 	//
 }
+
+func ExampleUserSettings_ConfigFinder() {
+	// This can be used to test SSH config parsing.
+	u := ssh_config.UserSettings{}
+	u.ConfigFinder(func() string {
+		return filepath.Join("testdata", "test_config")
+	})
+	u.Get("example.com", "Host")
+}