Added chomp interpolation function.

config/interpolate_funcs.go

@@ -58,6 +58,7 @@ func Funcs() map[string]ast.Function {
 		"base64encode": interpolationFuncBase64Encode(),
 		"base64sha256": interpolationFuncBase64Sha256(),
 		"ceil":         interpolationFuncCeil(),
+		"chomp":        interpolationFuncChomp(),
 		"cidrhost":     interpolationFuncCidrHost(),
 		"cidrnetmask":  interpolationFuncCidrNetmask(),
 		"cidrsubnet":   interpolationFuncCidrSubnet(),
@@ -459,6 +460,17 @@ func interpolationFuncCeil() ast.Function {
 	}
 }
 
+// interpolationFuncChomp removes trailing newlines from the given string
+func interpolationFuncChomp() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeString},
+		ReturnType: ast.TypeString,
+		Callback: func(args []interface{}) (interface{}, error) {
+			return strings.TrimRight(args[0].(string), "\n"), nil
+		},
+	}
+}
+
 // interpolationFuncFloorreturns returns the greatest integer value less than or equal to the argument
 func interpolationFuncFloor() ast.Function {
 	return ast.Function{

config/interpolate_funcs_test.go

@@ -370,6 +370,32 @@ func TestInterpolateFuncCeil(t *testing.T) {
 	})
 }
 
+func TestInterpolateFuncChomp(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Cases: []testFunctionCase{
+			{
+				`${chomp()}`,
+				nil,
+				true,
+			},
+
+			{
+				`${chomp("hello world")}`,
+				"hello world",
+				false,
+			},
+
+			{
+				`${chomp("goodbye\ncruel\nworld\n")}`,
+				`goodbye
+cruel
+world`,
+				false,
+			},
+		},
+	})
+}
+
 func TestInterpolateFuncMap(t *testing.T) {
 	testFunction(t, testFunctionConfig{
 		Cases: []testFunctionCase{

website/source/docs/configuration/interpolation.html.md

@@ -156,6 +156,8 @@ The supported built-in functions are:
   * `ceil(float)` - Returns the least integer value greater than or equal
       to the argument.
 
+  * `chomp(string)` - Removes trailing newlines from the given string.
+
   * `cidrhost(iprange, hostnum)` - Takes an IP address range in CIDR notation
     and creates an IP address with the given host number. For example,
     `cidrhost("10.0.0.0/8", 2)` returns `10.0.0.2`.