New counter flag type

```
-vvv
```

Will give a value of 3

```
-v=4 -v
```

Will give a value of 5

2 files changed, 139 insertions, 0 deletions

diff --git a/count.go b/count.go
new file mode 100644
index 0000000..d061368
--- /dev/null
+++ b/count.go
@@ -0,0 +1,84 @@
+package pflag
+
+import (
+	"fmt"
+	"strconv"
+)
+
+// -- count Value
+type countValue int
+
+func newCountValue(val int, p *int) *countValue {
+	*p = val
+	return (*countValue)(p)
+}
+
+func (i *countValue) Set(s string) error {
+	v, err := strconv.ParseInt(s, 0, 64)
+	// -1 means that no specific value was passed, so increment
+	if v == -1 {
+		*i = countValue(*i + 1)
+	} else {
+		*i = countValue(v)
+	}
+	return err
+}
+
+func (i *countValue) Type() string {
+	return "count"
+}
+
+func (i *countValue) String() string { return fmt.Sprintf("%v", *i) }
+
+func countConv(sval string) (interface{}, error) {
+	i, err := strconv.Atoi(sval)
+	if err != nil {
+		return nil, err
+	}
+	return i, nil
+}
+
+func (f *FlagSet) GetCount(name string) (int, error) {
+	val, err := f.getFlagType(name, "count", countConv)
+	if err != nil {
+		return 0, err
+	}
+	return val.(int), nil
+}
+
+func (f *FlagSet) CountVar(p *int, name string, usage string) {
+	f.CountVarP(p, name, "", usage)
+}
+
+func (f *FlagSet) CountVarP(p *int, name, shorthand string, usage string) {
+	flag := f.VarPF(newCountValue(0, p), name, shorthand, usage)
+	flag.NoOptDefVal = "-1"
+}
+
+func CountVar(p *int, name string, usage string) {
+	CommandLine.CountVar(p, name, usage)
+}
+
+func CountVarP(p *int, name, shorthand string, usage string) {
+	CommandLine.CountVarP(p, name, shorthand, usage)
+}
+
+func (f *FlagSet) Count(name string, usage string) *int {
+	p := new(int)
+	f.CountVarP(p, name, "", usage)
+	return p
+}
+
+func (f *FlagSet) CountP(name, shorthand string, usage string) *int {
+	p := new(int)
+	f.CountVarP(p, name, shorthand, usage)
+	return p
+}
+
+func Count(name string, usage string) *int {
+	return CommandLine.CountP(name, "", usage)
+}
+
+func CountP(name, shorthand string, usage string) *int {
+	return CommandLine.CountP(name, shorthand, usage)
+}
diff --git a/count_test.go b/count_test.go
new file mode 100644
index 0000000..716765c
--- /dev/null
+++ b/count_test.go
@@ -0,0 +1,55 @@
+package pflag
+
+import (
+	"fmt"
+	"os"
+	"testing"
+)
+
+var _ = fmt.Printf
+
+func setUpCount(c *int) *FlagSet {
+	f := NewFlagSet("test", ContinueOnError)
+	f.CountVarP(c, "verbose", "v", "a counter")
+	return f
+}
+
+func TestCount(t *testing.T) {
+	testCases := []struct {
+		input    []string
+		success  bool
+		expected int
+	}{
+		{[]string{"-vvv"}, true, 3},
+		{[]string{"-v", "-v", "-v"}, true, 3},
+		{[]string{"-v", "--verbose", "-v"}, true, 3},
+		{[]string{"-v=3", "-v"}, true, 4},
+		{[]string{"-v=a"}, false, 0},
+	}
+
+	devnull, _ := os.Open(os.DevNull)
+	os.Stderr = devnull
+	for i := range testCases {
+		var count int
+		f := setUpCount(&count)
+
+		tc := &testCases[i]
+
+		err := f.Parse(tc.input)
+		if err != nil && tc.success == true {
+			t.Errorf("expected success, got %q", err)
+			continue
+		} else if err == nil && tc.success == false {
+			t.Errorf("expected failure, got success")
+			continue
+		} else if tc.success {
+			c, err := f.GetCount("verbose")
+			if err != nil {
+				t.Errorf("Got error trying to fetch the counter flag")
+			}
+			if c != tc.expected {
+				t.Errorf("expected %q, got %q", tc.expected, c)
+			}
+		}
+	}
+}