Implementation of Git middleware

Defaults path to site root.

middleware/git/gitclient.go

@@ -0,0 +1,277 @@
+package git
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"strings"
+	"sync"
+	"time"
+)
+
+// DefaultInterval is the minimum interval to delay before
+// requesting another git pull
+const DefaultInterval time.Duration = time.Hour * 1
+
+// gitBinary holds the absolute path to git executable
+var gitBinary string
+
+// initMutex prevents parallel attempt to validate
+// git availability in PATH
+var initMutex sync.Mutex = sync.Mutex{}
+
+// Repo is the structure that holds required information
+// of a git repository.
+type Repo struct {
+	Url      string        // Repository URL
+	Path     string        // Directory to pull to
+	Host     string        // Git domain host e.g. github.com
+	Branch   string        // Git branch
+	KeyPath  string        // Path to private ssh key
+	Interval time.Duration // Interval between pulls
+	pulled   bool          // true if there is a successful pull
+	lastPull time.Time     // time of the last successful pull
+	sync.Mutex
+}
+
+// Pull requests a repository pull.
+// If it has been performed previously, it returns
+// and requests another pull in background.
+// Otherwise it waits until the pull is done.
+func (r *Repo) Pull() error {
+	// if site is not pulled, pull
+	if !r.pulled {
+		return pull(r)
+	}
+
+	// request pull in background
+	go pull(r)
+	return nil
+}
+
+// pull performs git clone, or git pull if repository exists
+func pull(r *Repo) error {
+	r.Lock()
+	defer r.Unlock()
+	// if it is less than interval since last pull, return
+	if time.Since(r.lastPull) <= r.Interval {
+		return nil
+	}
+
+	params := []string{"clone", "-b", r.Branch, r.Url, r.Path}
+	if r.pulled {
+		params = []string{"pull", "origin", r.Branch}
+	}
+
+	// if key is specified, pull using ssh key
+	if r.KeyPath != "" {
+		return pullWithKey(r, params)
+	}
+
+	cmd := exec.Command(gitBinary, params...)
+	cmd.Env = os.Environ()
+	cmd.Stdout = os.Stderr
+	cmd.Stderr = os.Stderr
+	if r.pulled {
+		cmd.Dir = r.Path
+	}
+
+	var err error
+	if err = cmd.Start(); err != nil {
+		return err
+	}
+
+	if err = cmd.Wait(); err == nil {
+		r.pulled = true
+		r.lastPull = time.Now()
+		log.Printf("%v pulled.\n", r.Url)
+	}
+
+	return err
+}
+
+// pullWithKey performs git clone or git pull if repository exists.
+// It is used for private repositories and requires an ssh key.
+// Note: currently only limited to Linux and OSX.
+func pullWithKey(r *Repo, params []string) error {
+	var gitSsh, script *os.File
+	// ensure temporary files deleted after usage
+	defer func() {
+		if gitSsh != nil {
+			os.Remove(gitSsh.Name())
+		}
+		if script != nil {
+			os.Remove(script.Name())
+		}
+	}()
+
+	var err error
+	// write git.sh script to temp file
+	gitSsh, err = writeScriptFile(gitWrapperScript(gitBinary))
+	if err != nil {
+		return err
+	}
+
+	// write git clone bash script to file
+	script, err = writeScriptFile(bashScript(gitSsh.Name(), r, params))
+	if err != nil {
+		return err
+	}
+
+	// execute the git clone bash script
+	cmd := exec.Command(script.Name())
+	cmd.Env = os.Environ()
+	cmd.Stdout = os.Stderr
+	cmd.Stderr = os.Stderr
+	if r.pulled {
+		cmd.Dir = r.Path
+	}
+
+	if err = cmd.Start(); err != nil {
+		return err
+	}
+
+	if err = cmd.Wait(); err == nil {
+		r.pulled = true
+		r.lastPull = time.Now()
+		log.Printf("%v pulled.\n", r.Url)
+	}
+	return err
+}
+
+// prepare prepares for a git pull
+// and validates the configured directory
+func prepare(r *Repo) error {
+	// check if directory exists or is empty
+	// if not, create directory
+	fs, err := ioutil.ReadDir(r.Path)
+	if err != nil || len(fs) == 0 {
+		return os.MkdirAll(r.Path, os.FileMode(0755))
+	}
+
+	// validate git repo
+	isGit := false
+	for _, f := range fs {
+		if f.IsDir() && f.Name() == ".git" {
+			isGit = true
+			break
+		}
+	}
+
+	if isGit {
+		// check if same repository
+		var repoUrl string
+		if repoUrl, err = getRepoUrl(r.Path); err == nil && repoUrl == r.Url {
+			r.pulled = true
+			return nil
+		}
+		if err != nil {
+			return fmt.Errorf("Cannot retrieve repo url for %v Error: %v", r.Path, err)
+		}
+		return fmt.Errorf("Another git repo '%v' exists at %v", repoUrl, r.Path)
+	}
+	return fmt.Errorf("Cannot git clone into %v, directory not empty.", r.Path)
+}
+
+// getRepoUrl retrieves remote origin url for the git repository at path
+func getRepoUrl(path string) (string, error) {
+	args := []string{"config", "--get", "remote.origin.url"}
+
+	_, err := os.Stat(path)
+	if err != nil {
+		return "", err
+	}
+
+	cmd := exec.Command(gitBinary, args...)
+	cmd.Dir = path
+	output, err := cmd.Output()
+	if err != nil {
+		return "", err
+	}
+
+	return strings.TrimSpace(string(output)), nil
+}
+
+// initGit validates git installation and locates the git executable
+// binary in PATH
+func initGit() error {
+	// prevent concurrent call
+	initMutex.Lock()
+	defer initMutex.Unlock()
+
+	// if validation has been done before and binary located in
+	// PATH, return.
+	if gitBinary != "" {
+		return nil
+	}
+
+	// locate git binary in path
+	var err error
+	gitBinary, err = exec.LookPath("git")
+	return err
+
+}
+
+// writeScriptFile writes content to a temporary file.
+// It changes the temporary file mode to executable and
+// closes it to prepare it for execution.
+func writeScriptFile(content []byte) (file *os.File, err error) {
+	if file, err = ioutil.TempFile("", "caddy"); err != nil {
+		return nil, err
+	}
+	if _, err = file.Write(content); err != nil {
+		return nil, err
+	}
+	if err = file.Chmod(os.FileMode(0755)); err != nil {
+		return nil, err
+	}
+	return file, file.Close()
+}
+
+// gitWrapperScript forms content for git.sh script
+var gitWrapperScript = func(gitBinary string) []byte {
+	return []byte(fmt.Sprintf(`#!/bin/bash
+
+# The MIT License (MIT)
+# Copyright (c) 2013 Alvin Abad
+
+if [ $# -eq 0 ]; then
+    echo "Git wrapper script that can specify an ssh-key file
+Usage:
+    git.sh -i ssh-key-file git-command
+    "
+    exit 1
+fi
+
+# remove temporary file on exit
+trap 'rm -f /tmp/.git_ssh.$$' 0
+
+if [ "$1" = "-i" ]; then
+    SSH_KEY=$2; shift; shift
+    echo "ssh -i $SSH_KEY \$@" > /tmp/.git_ssh.$$
+    chmod +x /tmp/.git_ssh.$$
+    export GIT_SSH=/tmp/.git_ssh.$$
+fi
+
+# in case the git command is repeated
+[ "$1" = "git" ] && shift
+
+# Run the git command
+%v "$@"
+
+`, gitBinary))
+}
+
+// bashScript forms content of bash script to clone or update a repo using ssh
+var bashScript = func(gitShPath string, repo *Repo, params []string) []byte {
+	return []byte(fmt.Sprintf(`#!/bin/bash
+
+mkdir -p ~/.ssh;
+touch ~/.ssh/known_hosts;
+ssh-keyscan -t rsa,dsa %v 2>&1 | sort -u - ~/.ssh/known_hosts > ~/.ssh/tmp_hosts;
+cat ~/.ssh/tmp_hosts >> ~/.ssh/known_hosts;
+%v -i %v %v;
+`, repo.Host, gitShPath, repo.KeyPath, strings.Join(params, " ")))
+}