Merge pull request #5: git-bundle-server CLI 4: complete basic subcommands

* Add `crontab` integration in the `init` subcommand. Initializes daily updates of the bundle lists.
* Add `start`, `stop`, and `delete` subcommands.

Author: derrickstolee

Diff for: cmd/git-bundle-server/cron.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/github/git-bundle-server/internal/core"
+)
+
+func SetCronSchedule() error {
+	pathToExec, err := os.Executable()
+	if err != nil {
+		return fmt.Errorf("failed to get executable: %w", err)
+	}
+
+	dailySchedule := "0 0 * * * \"" + pathToExec + "\" update-all\n"
+
+	scheduleBytes, err := core.LoadExistingSchedule()
+	if err != nil {
+		return fmt.Errorf("failed to get existing cron schedule: %w", err)
+	}
+
+	scheduleStr := string(scheduleBytes)
+
+	// TODO: Use comments to indicate a "region" where our schedule
+	// is set, so we can remove the entire region even if we update
+	// the schedule in the future.
+	if strings.Contains(scheduleStr, dailySchedule) {
+		// We already have this schedule, so skip modifying
+		// the crontab schedule.
+		return nil
+	}
+
+	scheduleBytes = append(scheduleBytes, []byte(dailySchedule)...)
+	scheduleFile := core.CrontabFile()
+
+	err = os.WriteFile(scheduleFile, scheduleBytes, 0o600)
+	if err != nil {
+		return fmt.Errorf("failed to write new cron schedule to temp file: %w", err)
+	}
+
+	err = core.CommitCronSchedule(scheduleFile)
+	if err != nil {
+		return fmt.Errorf("failed to commit new cron schedule: %w", err)
+	}
+
+	err = os.Remove(scheduleFile)
+	if err != nil {
+		return fmt.Errorf("failed to clear schedule file: %w", err)
+	}
+
+	return nil
+}

Diff for: cmd/git-bundle-server/delete.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"errors"
+	"os"
+
+	"github.com/github/git-bundle-server/internal/core"
+)
+
+type Delete struct{}
+
+func (Delete) subcommand() string {
+	return "delete"
+}
+
+func (Delete) run(args []string) error {
+	if len(args) < 1 {
+		return errors.New("usage: git-bundle-server delete <route>")
+	}
+
+	route := args[0]
+
+	repo, err := core.CreateRepository(route)
+	if err != nil {
+		return err
+	}
+
+	err = core.RemoveRoute(route)
+	if err != nil {
+		return err
+	}
+
+	err = os.RemoveAll(repo.WebDir)
+	if err != nil {
+		return err
+	}
+
+	err = os.RemoveAll(repo.RepoDir)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}

Diff for: cmd/git-bundle-server/init.go

@@ -63,5 +63,7 @@ func (Init) run(args []string) error {
 		return fmt.Errorf("failed to write bundle list: %w", listErr)
 	}
 
+	SetCronSchedule()
+
 	return nil
 }

Diff for: cmd/git-bundle-server/start.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"os"
+
+	"github.com/github/git-bundle-server/internal/core"
+)
+
+type Start struct{}
+
+func (Start) subcommand() string {
+	return "start"
+}
+
+func (Start) run(args []string) error {
+	if len(args) < 1 {
+		return errors.New("usage: git-bundle-server start <route>")
+	}
+
+	route := args[0]
+
+	// CreateRepository registers the route.
+	repo, err := core.CreateRepository(route)
+	if err != nil {
+		return err
+	}
+
+	_, err = os.ReadDir(repo.RepoDir)
+	if err != nil {
+		return fmt.Errorf("route '%s' appears to have been deleted; use 'init' instead", route)
+	}
+
+	// Make sure we have the global schedule running.
+	SetCronSchedule()
+
+	return nil
+}

Diff for: cmd/git-bundle-server/stop.go

@@ -0,0 +1,23 @@
+package main
+
+import (
+	"errors"
+
+	"github.com/github/git-bundle-server/internal/core"
+)
+
+type Stop struct{}
+
+func (Stop) subcommand() string {
+	return "stop"
+}
+
+func (Stop) run(args []string) error {
+	if len(args) < 1 {
+		return errors.New("usage: git-bundle-server stop <route>")
+	}
+
+	route := args[0]
+
+	return core.RemoveRoute(route)
+}

Diff for: cmd/git-bundle-server/subcommand.go

@@ -7,7 +7,10 @@ type Subcommand interface {
 
 func all() []Subcommand {
 	return []Subcommand{
+		Delete{},
 		Init{},
+		Start{},
+		Stop{},
 		Update{},
 		UpdateAll{},
 	}

Diff for: internal/core/cron.go

@@ -0,0 +1,64 @@
+package core
+
+import (
+	"bytes"
+	"fmt"
+	"os/exec"
+)
+
+func GetCrontabCommand(args ...string) (*exec.Cmd, error) {
+	crontab, err := exec.LookPath("crontab")
+	if err != nil {
+		return nil, fmt.Errorf("failed to find 'crontab' on the path: %w", err)
+	}
+
+	cmd := exec.Command(crontab, args...)
+	return cmd, nil
+}
+
+func LoadExistingSchedule() ([]byte, error) {
+	cmd, err := GetCrontabCommand("-l")
+	if err != nil {
+		return nil, err
+	}
+
+	buffer := bytes.Buffer{}
+	cmd.Stdout = &buffer
+
+	errorBuffer := bytes.Buffer{}
+	cmd.Stderr = &errorBuffer
+
+	err = cmd.Start()
+	if err != nil {
+		return nil, fmt.Errorf("crontab failed to start: %w", err)
+	}
+
+	err = cmd.Wait()
+	if err != nil {
+		return nil, fmt.Errorf("crontab returned a failure: %w\nstderr: %s", err, errorBuffer.String())
+	}
+
+	return buffer.Bytes(), nil
+}
+
+func CommitCronSchedule(filename string) error {
+	cmd, err := GetCrontabCommand(filename)
+	if err != nil {
+		return err
+	}
+
+	errorBuffer := bytes.Buffer{}
+	cmd.Stderr = &errorBuffer
+
+	err = cmd.Start()
+	if err != nil {
+		return fmt.Errorf("crontab failed to start: %w", err)
+	}
+
+	err = cmd.Wait()
+	if err != nil {
+		return fmt.Errorf("crontab returned a failure: %w\nstderr: %s", err, errorBuffer.String())
+	}
+
+	return nil
+}

Diff for: internal/core/paths.go

@@ -19,3 +19,7 @@ func webroot() string {
 func reporoot() string {
 	return bundleroot() + "git/"
 }
+
+func CrontabFile() string {
+	return bundleroot() + "cron-schedule"
+}

Diff for: internal/core/repo.go

@@ -49,6 +49,22 @@ func CreateRepository(route string) (*Repository, error) {
 	return &repo, nil
 }
 
+func RemoveRoute(route string) error {
+	repos, err := GetRepositories()
+	if err != nil {
+		return fmt.Errorf("failed to parse routes file")
+	}
+
+	_, contains := repos[route]
+	if !contains {
+		return fmt.Errorf("route '%s' is not registered", route)
+	}
+
+	delete(repos, route)
+
+	return WriteRouteFile(repos)
+}
+
 func WriteRouteFile(repos map[string]Repository) error {
 	dir := bundleroot()
 	routefile := dir + "/routes"
@@ -59,7 +75,7 @@ func WriteRouteFile(repos map[string]Repository) error {
 		contents = contents + routes + "\n"
 	}
 
-	return os.WriteFile(routefile, []byte(contents), 0600)
+	return os.WriteFile(routefile, []byte(contents), 0o600)
 }
 
 func GetRepositories() (map[string]Repository, error) {
@@ -68,7 +84,7 @@ func GetRepositories() (map[string]Repository, error) {
 	dir := bundleroot()
 	routefile := dir + "/routes"
 
-	file, err := os.OpenFile(routefile, os.O_RDONLY|os.O_CREATE, 0600)
+	file, err := os.OpenFile(routefile, os.O_RDONLY|os.O_CREATE, 0o600)
 	if err != nil {
 		// Assume that the file doesn't exist?
 		return repos, nil