New hub sync command to update local branches

Ported from my bash version over at
https://github.com/mislav/dotfiles/blob/370154a5adc482afd89606c126bcd18df2560013/bin/git-sync

Makefile

@@ -11,6 +11,7 @@ HELP_CMD = \
 	share/man/man1/hub-pull-request.1 \
 	share/man/man1/hub-release.1 \
 	share/man/man1/hub-issue.1 \
+	share/man/man1/hub-sync.1 \
 
 HELP_EXT = \
 	share/man/man1/hub-am.1 \

commands/runner.go

@@ -101,7 +101,10 @@ func (r *Runner) Execute() ExecError {
 		return execErr
 	}
 
-	err = git.Run(args.Command, args.Params...)
+	gitArgs := []string{args.Command}
+	gitArgs = append(gitArgs, args.Params...)
+
+	err = git.Run(gitArgs...)
 	return newExecError(err)
 }
 

commands/sync.go

@@ -0,0 +1,132 @@
+package commands
+
+import (
+	"fmt"
+	"os"
+	"regexp"
+	"strings"
+
+	"github.com/github/hub/git"
+	"github.com/github/hub/github"
+	"github.com/github/hub/ui"
+	"github.com/github/hub/utils"
+)
+
+var cmdSync = &Command{
+	Run:   sync,
+	Usage: "sync",
+	Long: `Fetch git objects from upstream and update branches.
+
+- If the local branch is outdated, fast-forward it;
+- If the local branch contains unpushed work, warn about it;
+- If the branch seems merged and its upstream branch was deleted, delete it.
+
+If a local branch doesn't have any upstream configuration, but has a
+same-named branch on the remote, treat that as its upstream branch.
+
+## See also:
+
+hub(1), git-fetch(1)
+`,
+}
+
+func init() {
+	CmdRunner.Use(cmdSync)
+}
+
+func sync(cmd *Command, args *Args) {
+	localRepo, err := github.LocalRepo()
+	utils.Check(err)
+
+	remote, err := localRepo.MainRemote()
+	utils.Check(err)
+
+	defaultBranch := localRepo.MasterBranch().ShortName()
+	fullDefaultBranch := fmt.Sprintf("refs/remotes/%s/%s", remote.Name, defaultBranch)
+	currentBranch := ""
+	if curBranch, err := localRepo.CurrentBranch(); err == nil {
+		currentBranch = curBranch.ShortName()
+	}
+
+	err = git.Spawn("fetch", "--prune", "--quiet", "--progress", remote.Name)
+	utils.Check(err)
+
+	branchToRemote := map[string]string{}
+	if lines, err := git.ConfigAll("branch.*.remote"); err == nil {
+		configRe := regexp.MustCompile(`^branch\.(.+?)\.remote (.+)`)
+
+		for _, line := range lines {
+			if matches := configRe.FindStringSubmatch(line); len(matches) > 0 {
+				branchToRemote[matches[1]] = matches[2]
+			}
+		}
+	}
+
+	branches, err := git.LocalBranches()
+	utils.Check(err)
+
+	var green,
+		lightGreen,
+		red,
+		lightRed,
+		resetColor string
+
+	if ui.IsTerminal(os.Stdout) {
+		green = "\033[32m"
+		lightGreen = "\033[32;1m"
+		red = "\033[31m"
+		lightRed = "\033[31;1m"
+		resetColor = "\033[0m"
+	}
+
+	for _, branch := range branches {
+		fullBranch := fmt.Sprintf("refs/heads/%s", branch)
+		remoteBranch := fmt.Sprintf("refs/remotes/%s/%s", remote.Name, branch)
+		gone := false
+
+		if branchToRemote[branch] == remote.Name {
+			if upstream, err := git.SymbolicFullName(fmt.Sprintf("%s@{upstream}", branch)); err == nil {
+				remoteBranch = upstream
+			} else {
+				remoteBranch = ""
+				gone = true
+			}
+		} else if !git.HasFile(strings.Split(remoteBranch, "/")...) {
+			remoteBranch = ""
+		}
+
+		if remoteBranch != "" {
+			diff, err := git.NewRange(fullBranch, remoteBranch)
+			utils.Check(err)
+
+			if diff.IsIdentical() {
+				continue
+			} else if diff.IsAncestor() {
+				if branch == currentBranch {
+					git.Quiet("merge", "--ff-only", "--quiet", remoteBranch)
+				} else {
+					git.Quiet("update-ref", fullBranch, remoteBranch)
+				}
+				ui.Printf("%sUpdated branch %s%s%s (was %s).\n", green, lightGreen, branch, resetColor, diff.A[0:7])
+			} else {
+				ui.Errorf("warning: `%s' seems to contain unpushed commits\n", branch)
+			}
+		} else if gone {
+			diff, err := git.NewRange(fullBranch, fullDefaultBranch)
+			utils.Check(err)
+
+			if diff.IsAncestor() {
+				if branch == currentBranch {
+					git.Quiet("checkout", "--quiet", defaultBranch)
+					currentBranch = defaultBranch
+				}
+				git.Quiet("branch", "-D", branch)
+				ui.Printf("%sDeleted branch %s%s%s (was %s).\n", red, lightRed, branch, resetColor, diff.A[0:7])
+			} else {
+				ui.Errorf("warning: `%s' was deleted on %s, but appears not merged into %s\n", branch, remote.Name, defaultBranch)
+			}
+		}
+	}
+
+	args.NoForward()
+}

git/git.go

@@ -165,6 +165,29 @@ func RefList(a, b string) ([]string, error) {
 	return output, nil
 }
 
+func NewRange(a, b string) (*Range, error) {
+	output, err := gitOutput("rev-parse", "-q", a, b)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Range{output[0], output[1]}, nil
+}
+
+type Range struct {
+	A string
+	B string
+}
+
+func (r *Range) IsIdentical() bool {
+	return strings.EqualFold(r.A, r.B)
+}
+
+func (r *Range) IsAncestor() bool {
+	cmd := gitCmd("merge-base", "--is-ancestor", r.A, r.B)
+	return cmd.Success()
+}
+
 func CommentChar() string {
 	char, err := Config("core.commentchar")
 	if err != nil {
@@ -209,7 +232,12 @@ func Config(name string) (string, error) {
 }
 
 func ConfigAll(name string) ([]string, error) {
-	lines, err := gitOutput(gitConfigCommand([]string{"--get-all", name})...)
+	mode := "--get-all"
+	if strings.Contains(name, "*") {
+		mode = "--get-regexp"
+	}
+
+	lines, err := gitOutput(gitConfigCommand([]string{mode, name})...)
 	if err != nil {
 		err = fmt.Errorf("Unknown config %s", name)
 	}
@@ -251,20 +279,19 @@ func Alias(name string) (string, error) {
 	return Config(fmt.Sprintf("alias.%s", name))
 }
 
-func Run(command string, args ...string) error {
-	cmd := cmd.New("git")
-
-	for _, v := range GlobalFlags {
-		cmd.WithArg(v)
-	}
-
-	cmd.WithArg(command)
+func Run(args ...string) error {
+	cmd := gitCmd(args...)
+	return cmd.Run()
+}
 
-	for _, a := range args {
-		cmd.WithArg(a)
-	}
+func Spawn(args ...string) error {
+	cmd := gitCmd(args...)
+	return cmd.Spawn()
+}
 
-	return cmd.Run()
+func Quiet(args ...string) bool {
+	cmd := gitCmd(args...)
+	return cmd.Success()
 }
 
 func IsGitDir(dir string) bool {
@@ -273,16 +300,18 @@ func IsGitDir(dir string) bool {
 	return cmd.Success()
 }
 
-func gitOutput(input ...string) (outputs []string, err error) {
-	cmd := cmd.New("git")
-
-	for _, v := range GlobalFlags {
-		cmd.WithArg(v)
+func LocalBranches() ([]string, error) {
+	lines, err := gitOutput("branch", "--list")
+	if err == nil {
+		for i, line := range lines {
+			lines[i] = strings.TrimPrefix(line, "* ")
+		}
 	}
+	return lines, err
+}
 
-	for _, i := range input {
-		cmd.WithArg(i)
-	}
+func gitOutput(input ...string) (outputs []string, err error) {
+	cmd := gitCmd(input...)
 
 	out, err := cmd.CombinedOutput()
 	for _, line := range strings.Split(out, "\n") {
@@ -294,3 +323,17 @@ func gitOutput(input ...string) (outputs []string, err error) {
 
 	return outputs, err
 }
+
+func gitCmd(args ...string) *cmd.Cmd {
+	cmd := cmd.New("git")
+
+	for _, v := range GlobalFlags {
+		cmd.WithArg(v)
+	}
+
+	for _, a := range args {
+		cmd.WithArg(a)
+	}
+
+	return cmd
+}

share/man/man1/hub.1.ronn

@@ -79,6 +79,9 @@ git but that are extended through hub, and custom ones that hub provides.
   * hub-release(1):
     List and create GitHub releases.
 
+  * hub-sync(1):
+    Fetch from upstream and update local branches.
+
 ## CONFIGURATION
 
 ### GitHub OAuth authentication