1 files changed, 136 insertions, 0 deletions
diff --git a/plumbing/format/packp/capabilities.go b/plumbing/format/packp/capabilities.go
new file mode 100644
index 0000000..d77c2fa
--- /dev/null
+++ b/plumbing/format/packp/capabilities.go
@@ -0,0 +1,136 @@
+package packp
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+)
+
+// Capabilities contains all the server capabilities
+// https://github.com/git/git/blob/master/Documentation/technical/protocol-capabilities.txt
+type Capabilities struct {
+	m map[string]*Capability
+	o []string
+}
+
+// Capability represents a server capability
+type Capability struct {
+	Name   string
+	Values []string
+}
+
+// NewCapabilities returns a new Capabilities struct
+func NewCapabilities() *Capabilities {
+	return &Capabilities{
+		m: make(map[string]*Capability),
+	}
+}
+
+func (c *Capabilities) IsEmpty() bool {
+	return len(c.o) == 0
+}
+
+// Decode decodes a string
+func (c *Capabilities) Decode(raw string) {
+	params := strings.Split(raw, " ")
+	for _, p := range params {
+		s := strings.SplitN(p, "=", 2)
+
+		var value string
+		if len(s) == 2 {
+			value = s[1]
+		}
+
+		c.Add(s[0], value)
+	}
+}
+
+// Get returns the values for a capability
+func (c *Capabilities) Get(capability string) *Capability {
+	return c.m[capability]
+}
+
+// Set sets a capability removing the values
+func (c *Capabilities) Set(capability string, values ...string) {
+	if _, ok := c.m[capability]; ok {
+		delete(c.m, capability)
+	}
+
+	c.Add(capability, values...)
+}
+
+// Add adds a capability, values are optional
+func (c *Capabilities) Add(capability string, values ...string) {
+	if !c.Supports(capability) {
+		c.m[capability] = &Capability{Name: capability}
+		c.o = append(c.o, capability)
+	}
+
+	if len(values) == 0 {
+		return
+	}
+
+	c.m[capability].Values = append(c.m[capability].Values, values...)
+}
+
+// Supports returns true if capability is present
+func (c *Capabilities) Supports(capability string) bool {
+	_, ok := c.m[capability]
+	return ok
+}
+
+// SymbolicReference returns the reference for a given symbolic reference
+func (c *Capabilities) SymbolicReference(sym string) string {
+	if !c.Supports("symref") {
+		return ""
+	}
+
+	for _, symref := range c.Get("symref").Values {
+		parts := strings.Split(symref, ":")
+		if len(parts) != 2 {
+			continue
+		}
+
+		if parts[0] == sym {
+			return parts[1]
+		}
+	}
+
+	return ""
+}
+
+// Sorts capabilities in increasing order of their name
+func (c *Capabilities) Sort() {
+	sort.Strings(c.o)
+}
+
+func (c *Capabilities) String() string {
+	if len(c.o) == 0 {
+		return ""
+	}
+
+	var o string
+	for _, key := range c.o {
+		cap := c.m[key]
+
+		added := false
+		for _, value := range cap.Values {
+			if value == "" {
+				continue
+			}
+
+			added = true
+			o += fmt.Sprintf("%s=%s ", key, value)
+		}
+
+		if len(cap.Values) == 0 || !added {
+			o += key + " "
+		}
+	}
+
+	if len(o) == 0 {
+		return o
+	}
+
+	return o[:len(o)-1]
+}