From b4c56217ee1f45168f10df968d2f547ac8cee307 Mon Sep 17 00:00:00 2001
From: Jingwen Owen Ou <jingweno@gmail.com>
Date: Sun, 2 Jun 2013 17:04:25 -0700
Subject: [PATCH] Implement gh compare

---
 commands/browse.go       |  8 +------
 commands/commands.go     |  1 +
 commands/compare.go      | 52 ++++++++++++++++++++++++++++++++++++++++
 commands/compare_test.go | 14 +++++++++++
 commands/utils.go        | 17 +++++++++++++
 5 files changed, 85 insertions(+), 7 deletions(-)
 create mode 100644 commands/compare.go
 create mode 100644 commands/compare_test.go
 create mode 100644 commands/utils.go

diff --git a/commands/browse.go b/commands/browse.go
index 4bcaa18e..a9cebf14 100644
--- a/commands/browse.go
+++ b/commands/browse.go
@@ -1,7 +1,6 @@
 package commands
 
 import (
-	"github.com/jingweno/gh/cmd"
 	"github.com/jingweno/gh/github"
 	"github.com/jingweno/gh/utils"
 )
@@ -27,9 +26,6 @@ func init() {
 }
 
 func browse(command *Command, args []string) {
-	launcher, err := utils.BrowserLauncher()
-	utils.Check(err)
-
 	project := github.CurrentProject()
 	if flagBrowseSubpage == "tree" || flagBrowseSubpage == "commits" {
 		repo := project.LocalRepo()
@@ -37,8 +33,6 @@ func browse(command *Command, args []string) {
 	}
 
 	url := project.WebUrl(flagBrowseRepo, flagBrowseUser, flagBrowseSubpage)
-	launcher = append(launcher, url)
-	c := cmd.NewWithArray(launcher)
-	err = c.Exec()
+	err := browserCommand(url)
 	utils.Check(err)
 }
diff --git a/commands/commands.go b/commands/commands.go
index 4a9d9c61..463616cb 100644
--- a/commands/commands.go
+++ b/commands/commands.go
@@ -43,6 +43,7 @@ var All = []*Command{
 	cmdPullRequest,
 	cmdCiStatus,
 	cmdBrowse,
+	cmdCompare,
 	cmdHelp,
 	cmdVersion,
 }
diff --git a/commands/compare.go b/commands/compare.go
new file mode 100644
index 00000000..8a0879d9
--- /dev/null
+++ b/commands/compare.go
@@ -0,0 +1,52 @@
+package commands
+
+import (
+	"fmt"
+	"github.com/jingweno/gh/github"
+	"github.com/jingweno/gh/utils"
+	"regexp"
+)
+
+var cmdCompare = &Command{
+	Run:   compare,
+	Usage: "compare [-u USER] [START...] END",
+	Short: "Open a compare page on GitHub",
+	Long: `Open a GitHub compare view page in the system's default web browser.
+START to END are branch names, tag names, or commit SHA1s specifying
+the range of history to compare. If a range with two dots (a..b) is given,
+it will be transformed into one with three dots. If START is omitted,
+GitHub will compare against the base branch (the default is "master").
+`,
+}
+
+var flagCompareUser string
+
+func init() {
+	cmdCompare.Flag.StringVar(&flagCompareUser, "u", "", "USER")
+}
+
+func compare(command *Command, args []string) {
+	project := github.CurrentProject()
+
+	var r string
+	if len(args) == 0 {
+		repo := project.LocalRepo()
+		r = repo.Head
+	} else {
+		r = args[0]
+	}
+
+	r = transformToTripleDots(r)
+	subpage := utils.ConcatPaths("compare", r)
+	url := project.WebUrl("", flagCompareUser, subpage)
+	err := browserCommand(url)
+	utils.Check(err)
+}
+
+func transformToTripleDots(r string) string {
+	ownerRe := "[a-zA-Z0-9][a-zA-Z0-9-]*"
+	shaOrTag := fmt.Sprintf("((?:%s:)?\\w[\\w.-]+\\w)", ownerRe)
+	shaOrTagRange := fmt.Sprintf("^%s\\.\\.%s$", shaOrTag, shaOrTag)
+	shaOrTagRangeRegexp := regexp.MustCompile(shaOrTagRange)
+	return shaOrTagRangeRegexp.ReplaceAllString(r, "$1...$2")
+}
diff --git a/commands/compare_test.go b/commands/compare_test.go
new file mode 100644
index 00000000..4e41b741
--- /dev/null
+++ b/commands/compare_test.go
@@ -0,0 +1,14 @@
+package commands
+
+import (
+	"github.com/bmizerany/assert"
+	"testing"
+)
+
+func TestTransformToTripleDots(t *testing.T) {
+	s := "1.0..2.0"
+	assert.Equal(t, "1.0...2.0", transformToTripleDots(s))
+
+	s = "1.0...2.0"
+	assert.Equal(t, "1.0...2.0", transformToTripleDots(s))
+}
diff --git a/commands/utils.go b/commands/utils.go
new file mode 100644
index 00000000..206d5e3f
--- /dev/null
+++ b/commands/utils.go
@@ -0,0 +1,17 @@
+package commands
+
+import (
+	"github.com/jingweno/gh/cmd"
+	"github.com/jingweno/gh/utils"
+)
+
+func browserCommand(url string) error {
+	launcher, err := utils.BrowserLauncher()
+	if err != nil {
+		return err
+	}
+
+	launcher = append(launcher, url)
+	c := cmd.NewWithArray(launcher)
+	return c.Exec()
+}