Add a function that can reload config files

README.md

@@ -42,6 +42,16 @@ Some SSH arguments have default values - for example, the default value for
 given Host/keyword pair exists in the config, we'll return a default for the
 keyword if one exists.
 
+### Reloading SSH config files
+Once the first call to `Get()`, `GetStrict()`, `GetAll()`, or `GetAllStrict()`
+has been made, the contents of the config files will be cached for all future
+calls to any of those functions. The `ReloadConfigs()` function will reset
+this cache and replace it with the current config file contents.
+
+```go
+ssh_config.ReloadConfigs()
+```
+
 ### Manipulating SSH config files
 
 Here's how you can manipulate an SSH config file, and then write it back to

config.go

@@ -8,7 +8,7 @@
 // the host name to match on ("example.com"), and the second argument is the key
 // you want to retrieve ("Port"). The keywords are case insensitive.
 //
-// 		port := ssh_config.Get("myhost", "Port")
+//	port := ssh_config.Get("myhost", "Port")
 //
 // You can also manipulate an SSH config file and then print it or write it back
 // to disk.
@@ -59,7 +59,7 @@ type UserSettings struct {
 	systemConfigFinder configFinder
 	userConfig         *Config
 	userConfigFinder   configFinder
-	loadConfigs        sync.Once
+	loadConfigs        *sync.Once
 	onceErr            error
 }
 
@@ -167,6 +167,14 @@ func GetAllStrict(alias, key string) ([]string, error) {
 	return DefaultUserSettings.GetAllStrict(alias, key)
 }
 
+// ReloadConfigs clears the cached config data and freshly loads the config
+// files again.
+//
+// ReloadConfigs is a wrapper around DefaultUserSettings.ReloadConfigs.
+func ReloadConfigs() {
+	DefaultUserSettings.ReloadConfigs()
+}
+
 // Get finds the first value for key within a declaration that matches the
 // alias. Get returns the empty string if no value was found, or if IgnoreErrors
 // is false and we could not parse the configuration file. Use GetStrict to
@@ -272,6 +280,9 @@ func (u *UserSettings) ConfigFinder(f func() string) {
 }
 
 func (u *UserSettings) doLoadConfigs() {
+	if u.loadConfigs == nil {
+		u.loadConfigs = new(sync.Once)
+	}
 	u.loadConfigs.Do(func() {
 		var filename string
 		var err error
@@ -310,6 +321,13 @@ func (u *UserSettings) doLoadConfigs() {
 	})
 }
 
+// ReloadConfigs clears the cached config data and freshly loads the config
+// files again.
+func (u *UserSettings) ReloadConfigs() {
+	u.loadConfigs = new(sync.Once)
+	u.doLoadConfigs()
+}
+
 func parseFile(filename string) (*Config, error) {
 	return parseWithDepth(filename, 0)
 }

config_test.go

@@ -259,6 +259,72 @@ func TestGetEqsign(t *testing.T) {
 	}
 }
 
+var modified1 = []byte(`
+Host wap
+  User modified1
+  KexAlgorithms diffie-hellman-group1-sha1
+`)
+
+var modified2 = []byte(`
+Host wap
+  User modified2
+  KexAlgorithms diffie-hellman-group1-sha1
+`)
+
+func TestCachedConfig(t *testing.T) {
+	us := &UserSettings{
+		userConfigFinder: testConfigFinder("testdata/modified"),
+	}
+
+	err1 := os.WriteFile("testdata/modified", modified1, 0644)
+	if err1 != nil {
+		t.Errorf("error writing to file: %v", err1)
+	}
+
+	val1 := us.Get("wap", "User")
+	if val1 != "modified1" {
+		t.Errorf("expected to find User modified1, got %q", val1)
+	}
+
+	err2 := os.WriteFile("testdata/modified", modified2, 0644)
+	if err1 != nil {
+		t.Errorf("error writing to file: %v", err2)
+	}
+
+	val2 := us.Get("wap", "User")
+	if val2 != "modified1" {
+		t.Errorf("expected to find User modified1, got %q", val2)
+	}
+}
+
+func TestReloadConfigs(t *testing.T) {
+	us := &UserSettings{
+		userConfigFinder: testConfigFinder("testdata/modified"),
+	}
+
+	err1 := os.WriteFile("testdata/modified", modified1, 0644)
+	if err1 != nil {
+		t.Errorf("error writing to file: %v", err1)
+	}
+
+	val1 := us.Get("wap", "User")
+	if val1 != "modified1" {
+		t.Errorf("expected to find User modified1, got %q", val1)
+	}
+
+	err2 := os.WriteFile("testdata/modified", modified2, 0644)
+	if err1 != nil {
+		t.Errorf("error writing to file: %v", err2)
+	}
+
+	us.ReloadConfigs()
+
+	val2 := us.Get("wap", "User")
+	if val2 != "modified2" {
+		t.Errorf("expected to find User modified2, got %q", val2)
+	}
+}
+
 var includeFile = []byte(`
 # This host should not exist, so we can use it for test purposes / it won't
 # interfere with any other configurations.

testdata/modified

@@ -0,0 +1,4 @@
+
+Host wap
+  User modified2
+  KexAlgorithms diffie-hellman-group1-sha1