add support for github -> local sync

2 files changed, 176 insertions, 56 deletions

diff --git a/update.py b/update.py
index 80334f5..8d2c207 100755
--- a/update.py
+++ b/update.py
@@ -1,69 +1,122 @@
 #!/usr/bin/python3
 import sys, os, subprocess, argparse
+import configparser, itertools, json, re
+import traceback
+import email.mime.text, email.utils, smtplib
 
 class GitCommand:
     def __getattr__(self, name):
-        def call(*args, get_stderr = False):
+        def call(*args, capture_stderr = False, check = True):
+            '''If <capture_stderr>, return stderr merged with stdout. Otherwise, return stdout and forward stderr to our own.
+               If <check> is true, throw an exception of the process fails with non-zero exit code. Otherwise, do not.
+               In any case, return a pair of the captured output and the exit code.'''
             cmd = ["git", name.replace('_', '-')] + list(args)
-            output = subprocess.check_output(cmd, stderr=subprocess.STDOUT if get_stderr else None)
-            return output.decode('utf-8').strip('\n')
+            with subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT if capture_stderr else None) as p:
+                (stdout, stderr) = p.communicate()
+                assert stderr is None
+                code = p.returncode
+                if check and code:
+                    raise Exception("Error running {0}: Non-zero exit code".format(cmd))
+            return (stdout.decode('utf-8').strip('\n'), code)
         return call
 
-    def branches(self, *args):
-        b = self.branch(*args).split('\n')
-        b = map(lambda s: s[2:], b)
-        return list(b)
-
 git = GitCommand()
 
-def is_all_zero(str):
-    return len(str.replace('0', '')) == 0
+def read_config(fname, defSection = 'DEFAULT'):
+    '''Reads a config file that may have options outside of any section.'''
+    config = configparser.ConfigParser()
+    with open(fname) as file:
+        stream = itertools.chain(("["+defSection+"]\n",), file)
+        config.read_file(stream)
+    return config
+
+def send_mail(subject, text, receivers, sender='post+webhook@ralfj.de', replyTo=None):
+    assert isinstance(receivers, list)
+    if not len(receivers): return # nothing to do
+    # construct content
+    msg = email.mime.text.MIMEText(text.encode('UTF-8'), 'plain', 'UTF-8')
+    msg['Subject'] = subject
+    msg['Date'] = email.utils.formatdate(localtime=True)
+    msg['From'] = sender
+    msg['To'] = ', '.join(receivers)
+    if replyTo is not None:
+        msg['Reply-To'] = replyTo
+    # put into envelope and send
+    s = smtplib.SMTP('localhost')
+    s.sendmail(sender, receivers, msg.as_string())
+    s.quit()
+
+def get_github_payload():
+    '''Reeturn the github-style JSON encoded payload (as if we were called as a github webhook)'''
+    try:
+        data = sys.stdin.buffer.read()
+        data = json.loads(data.decode('utf-8'))
+        return data
+    except:
+        return {} # nothing read
 
 class Repo:
-    def __init__(self, local, mirrors):
-        '''<local> is the directory containing the repository locally, <mirrors> a list of remote repositories'''
-        self.local = local
-        self.mirrors = mirrors
+    def __init__(self, conf):
+        '''Creates a repository from a section of the git-mirror configuration file'''
+        self.local = conf['local']
+        self.mirrors = {} # maps mirrors to their URLs
+        mirror_prefix = 'mirror-'
+        for name in filter(lambda s: s.startswith(mirror_prefix), conf.keys()):
+            mirror = name[len(mirror_prefix):]
+            self.mirrors[mirror] = conf[name]
+    
+    def find_mirror_by_url(self, match_urls):
+        for mirror, url in self.mirrors.items():
+            if url in match_urls:
+                return mirror
+        return None
 
-#    This is old code, that may be useful again if we decide to care about racy pushes loosing commits.
-#    def pull(self, slavenr):
-#        slave = self.slaves[slavenr]
-#        slavename = "slave-"+str(slavenr)
-#        # make sure we have the remote
-#        try:
-#            git.remote("add", slavename, slave, get_stderr=True)
-#        except subprocess.CalledProcessError: # the remote already exists
-#            git.remote("set-url", slavename, slave)
-#        # get all the changes
-#        git.fetch(slavename, get_stderr=True)
-#        # merge them... or hope so...
-#        branches = git.branches("-r")
-#        for branch in filter(lambda s: s.startswith(slavename+"/"), branches):
-#            local = branch[len(slavename+"/"):]
-#            print(local, branch)
+    def have_ref(self, ref, url=None):
+        '''Tests if a given ref exists, locally or (if the url is given) remotely'''
+        if url is None:
+            out, code = git.show_ref(ref, check = False)
+            if code and len(out):
+                raise Exception("Checking for a local ref failed")
+        else:
+            out, code = git.ls_remote(url, ref)
+        # the ref exists iff we have output
+        return len(out) > 0
     
-    def update_mirror_ref(self, ref, mirror):
-        '''Update <ref> on <mirror> to the local state. If <newsha> is all-zero, the ref should be deleted.'''
-        git.push('--force', self.mirrors[mirror], ref)
+    def update_mirrors(self, ref, delete, exception = None, suppress_stderr = False):
+        '''Update <ref> on all mirrors except for <exception> to the local state, or delete it.'''
+        for mirror in self.mirrors:
+            if mirror == exception:
+                continue
+            # update this mirror
+            if not self.have_ref(ref):
+                # delete ref remotely
+                git.push(self.mirrors[mirror], ':'+ref, capture_stderr = suppress_stderr)
+            else:
+                # update ref remotely
+                git.push('--force', self.mirrors[mirror], ref, capture_stderr = suppress_stderr)
     
-    def update_ref(self, newsha, ref, source):
-        '''Update the <ref> to <newsha> everywhere. <source> is None if this update comes from the local repository,
-           or the name of a mirror. If <newsha> is all-zero, the ref should be deleted.'''
+    def update_ref(self, ref, source, suppress_stderr = False):
+        '''Update the <ref> to its state in <source> everywhere. <source> is None to refer to the local repository,
+           or the name of a mirror.'''
         os.chdir(self.local)
         if source is None:
             # We already have the latest version locally. Update all the mirrors.
-            for mirror in self.mirrors:
-                self.update_mirror_ref(ref, mirror)
+            self.update_mirrors(ref, delete = not self.have_ref(ref), suppress_stderr = suppress_stderr)
         else:
-            raise Exception("Help, what should I do?")
-
-# for now, configuration is hard-coded here...
-
-repos = {
-    'sync-test': Repo('/home/git/repositories/test.git', {'github': 'git@github.com:RalfJung/sync-test.git'}),
-}
+            # update our version of this ref. This may fail if the ref does not exist anymore.
+            url = self.mirrors[source]
+            if not self.have_ref(ref, url):
+                # delete ref locally
+                git.update_ref("-d", ref)
+                # and everywhere (except for the source)
+                self.update_mirrors(ref, delete = True, exception = source, suppress_stderr = suppress_stderr)
+            else:
+                # update local ref to remote state (yes, there's a race condition here - the ref could no longer exist by now)
+                git.fetch(url, ref+":"+ref)
+                # and everywhere else
+                self.update_mirrors(ref, delete = False, exception = source, suppress_stderr = suppress_stderr)
 
-def find_repo_by_directory(dir):
+def find_repo_by_directory(repos, dir):
     for (name, repo) in repos.items():
         if dir == repo.local:
             return name
@@ -71,26 +124,71 @@ def find_repo_by_directory(dir):
 
 if __name__ == "__main__":
     parser = argparse.ArgumentParser(description='Keep git repositories in sync')
-    parser.add_argument("--hook",
-                        action="store_true", dest="hook",
-                        help="Act as git hook: Auto-detect the repository based on the working directoy, and fetch information from stdin")
+    parser.add_argument("--git-hook",
+                        action="store_true", dest="git_hook",
+                        help="Act as git hook: Auto-detect the repository based on the working directoy, and fetch information from stdin the way git encodes it")
+    parser.add_argument("--web-hook",
+                        action="store_true", dest="web_hook",
+                        help="Act as github-style web hook: Repository has to be given explicitly, all the rest is read from stdin JSON form")
     parser.add_argument("-r", "--repository",
                         dest="repository",
                         help="The name of the repository to act on")
     args = parser.parse_args()
+    if args.git_hook and args.web_hook:
+        raise Exception("I cannot be two hooks at once.")
     
+    try:
+        # All arguments are *untrusted* input, as we may be called via sudo from the webserver. So we fix the configuration file location.
+        conffile = os.path.join(os.path.dirname(__file__), 'git-mirror.conf')
+        conf = read_config(conffile)
+        repos = {}
+        for name, section in conf.items():
+            if name != 'DEFAULT':
+                repos[name] = Repo(section)
+        
+        # find the repository we are dealing with
         reponame = args.repository
-    if reponame is None and args.hook:
-        reponame = find_repo_by_directory(os.getcwd())
-    if reponame is None:
-        raise Exception("Unable to detect repository, please use --repository.")
+        if reponame is None and args.git_hook:
+            reponame = find_repo_by_directory(repos, os.getcwd())
+        if reponame is None or reponame not in repos:
+            raise Exception("Unknown or missing repository name.")
         
         # now sync this repository
         repo = repos[reponame]
-    if args.hook:
+        if args.git_hook:
             # parse the information we get from stdin
             for line in sys.stdin:
                 (oldsha, newsha, ref) = line.split()
-            repo.update_ref(newsha, ref, source=None)
+                repo.update_ref(ref, source = None)
+        elif args.web_hook:
+            data = get_github_payload()
+            ref = data["ref"]
+            # validate the ref name
+            if re.match('refs/[a-z/]+', ref) is None:
+                raise Exception("Invalid ref name {0}".format(ref))
+            # collect URLs of this repository
+            urls = []
+            for key in ("git_url", "ssh_url", "clone_url"):
+                urls.append(data["repository"][key])
+            source = repo.find_mirror_by_url(urls)
+            if source is None:
+                raise Exception("Could not find the source.")
+            repo.update_ref(ref, source = source, suppress_stderr = True)
+            # print an answer
+            print("Content-Type: text/plain")
+            print()
+            print("Updated {0}:{1} from source {2}".format(reponame, ref, source))
+        else:
+            raise Exception("No manual mode is implemented so far.")
+    except Exception as e:
+        # don't leak filenames etc. when we are running as a hook
+        if args.web_hook:
+            print("Status: 500 Internal Server Error")
+            print("Content-Type: text/plain")
+            print()
+            print(str(e))
+        elif args.git_hook:
+            #sys.stderr.write(str(e))
+            traceback.print_exc()
         else:
-        raise Exception("I am unsure what to do here.")
+            traceback.print_exc()
diff --git a/webhook.py b/webhook.py
new file mode 100755
index 0000000..a7ae5f8
--- /dev/null
+++ b/webhook.py
@@ -0,0 +1,22 @@
+#!/usr/bin/python3
+import urllib.request, urllib.parse, json, os, sys
+
+def is_github(remote_addr):
+    '''Returns whether the address is a github hook address. This function requires Python 3.3.'''
+    from ipaddress import ip_address, ip_network
+    remote_addr = ip_address(ip_network)
+    github = urllib.request.urlopen('https://api.github.com/meta').read()
+    github = json.loads(github.decode('utf-8'))
+    for net in github['hooks']:
+        if remote_addr in ip_network(net):
+            return True
+
+# get repository from query string
+query = os.getenv("QUERY_STRING")
+query = urllib.parse.parse_qs(query)
+repository = query.get('repository', [])
+repository = repository[0] if len(repository) else ''
+
+# execute the actual script
+git_mirror = "/home/ralf/git-mirror/update.py"
+os.execlp("sudo", "sudo", "-n", "-u", "git", git_mirror, "--web-hook", "--repository", repository)