1 files changed, 42 insertions, 9 deletions
diff --git a/plumbing/format/config/option.go b/plumbing/format/config/option.go
index 3c391c6..d4775e4 100644
--- a/plumbing/format/config/option.go
+++ b/plumbing/format/config/option.go
@@ -1,6 +1,7 @@
 package config
 
 import (
+	"fmt"
 	"strings"
 )
 
@@ -21,6 +22,15 @@ func (o *Option) IsKey(key string) bool {
 	return strings.ToLower(o.Key) == strings.ToLower(key)
 }
 
+func (opts Options) GoString() string {
+	var strs []string
+	for _, opt := range opts {
+		strs = append(strs, fmt.Sprintf("%#v", opt))
+	}
+
+	return strings.Join(strs, ", ")
+}
+
 // Get gets the value for the given key if set,
 // otherwise it returns the empty string.
 //
@@ -69,16 +79,39 @@ func (opts Options) withAddedOption(key string, value string) Options {
 	return append(opts, &Option{key, value})
 }
 
-func (opts Options) withSettedOption(key string, value string) Options {
-	for i := len(opts) - 1; i >= 0; i-- {
-		o := opts[i]
-		if o.IsKey(key) {
-			result := make(Options, len(opts))
-			copy(result, opts)
-			result[i] = &Option{key, value}
-			return result
+func (opts Options) withSettedOption(key string, values ...string) Options {
+	var result Options
+	var added []string
+	for _, o := range opts {
+		if !o.IsKey(key) {
+			result = append(result, o)
+			continue
+		}
+
+		if contains(values, o.Value) {
+			added = append(added, o.Value)
+			result = append(result, o)
+			continue
+		}
+	}
+
+	for _, value := range values {
+		if contains(added, value) {
+			continue
+		}
+
+		result = result.withAddedOption(key, value)
+	}
+
+	return result
+}
+
+func contains(haystack []string, needle string) bool {
+	for _, s := range haystack {
+		if s == needle {
+			return true
 		}
 	}
 
-	return opts.withAddedOption(key, value)
+	return false
 }