Issue #195: Move doc generation into separate pkg

* Move man_docs and md_docs into new doc pkg
* Replace *bytes.Buffer with io.Writer
* Replace c == cmd.helpCommand with c.IsHelpCommand()
* Remove redundant len(children) == 0 check in HasSeeAlso
* Duplicate test setup for doc generation

doc/man_docs_test.go

@@ -0,0 +1,93 @@
+package doc
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"strings"
+	"testing"
+)
+
+var _ = fmt.Println
+var _ = os.Stderr
+
+func translate(in string) string {
+	return strings.Replace(in, "-", "\\-", -1)
+}
+
+func TestGenManDoc(t *testing.T) {
+	c := initializeWithRootCmd()
+	// Need two commands to run the command alphabetical sort
+	cmdEcho.AddCommand(cmdTimes, cmdEchoSub, cmdDeprecated)
+	c.AddCommand(cmdPrint, cmdEcho)
+	cmdRootWithRun.PersistentFlags().StringVarP(&flags2a, "rootflag", "r", "two", strtwoParentHelp)
+
+	out := new(bytes.Buffer)
+
+	header := &GenManHeader{
+		Title:   "Project",
+		Section: "2",
+	}
+	// We generate on a subcommand so we have both subcommands and parents
+	GenMan(cmdEcho, header, out)
+	found := out.String()
+
+	// Make sure parent has - in CommandPath() in SEE ALSO:
+	parentPath := cmdEcho.Parent().CommandPath()
+	dashParentPath := strings.Replace(parentPath, " ", "-", -1)
+	expected := translate(dashParentPath)
+	expected = expected + "(" + header.Section + ")"
+	checkStringContains(t, found, expected)
+
+	// Our description
+	expected = translate(cmdEcho.Name())
+	checkStringContains(t, found, expected)
+
+	// Better have our example
+	expected = translate(cmdEcho.Name())
+	checkStringContains(t, found, expected)
+
+	// A local flag
+	expected = "boolone"
+	checkStringContains(t, found, expected)
+
+	// persistent flag on parent
+	expected = "rootflag"
+	checkStringContains(t, found, expected)
+
+	// We better output info about our parent
+	expected = translate(cmdRootWithRun.Name())
+	checkStringContains(t, found, expected)
+
+	// And about subcommands
+	expected = translate(cmdEchoSub.Name())
+	checkStringContains(t, found, expected)
+
+	unexpected := translate(cmdDeprecated.Name())
+	checkStringOmits(t, found, unexpected)
+
+	// auto generated
+	expected = translate("Auto generated")
+	checkStringContains(t, found, expected)
+}
+
+func TestGenManNoGenTag(t *testing.T) {
+	c := initializeWithRootCmd()
+	// Need two commands to run the command alphabetical sort
+	cmdEcho.AddCommand(cmdTimes, cmdEchoSub, cmdDeprecated)
+	c.AddCommand(cmdPrint, cmdEcho)
+	cmdRootWithRun.PersistentFlags().StringVarP(&flags2a, "rootflag", "r", "two", strtwoParentHelp)
+	cmdEcho.DisableAutoGenTag = true
+	out := new(bytes.Buffer)
+
+	header := &GenManHeader{
+		Title:   "Project",
+		Section: "2",
+	}
+	// We generate on a subcommand so we have both subcommands and parents
+	GenMan(cmdEcho, header, out)
+	found := out.String()
+
+	unexpected := translate("#HISTORY")
+	checkStringOmits(t, found, unexpected)
+}