remote-helpers: add testgit helper

Currently the remote helper infrastructure is only used by the curl
helper, which does not give a good impression of how remote helpers
can be used to interact with foreign repositories. Since implementing
such a helper is non-trivial it would be good to have at least one
easy-to-follow example demonstrating how to implement a helper that
interacts with a foreign vcs using fast-import/fast-export.

The testgit helper can be used to interact with remote git
repositories by prefixing the url with "testgit::".

Signed-off-by: Junio C Hamano <gitster@pobox.com>

4 files changed, 220 insertions, 0 deletions

diff --git a/git_remote_helpers/git/exporter.py b/git_remote_helpers/git/exporter.py
new file mode 100644
index 0000000000..dfaab00b5f
--- /dev/null
+++ b/git_remote_helpers/git/exporter.py
@@ -0,0 +1,51 @@
+import os
+import subprocess
+import sys
+
+
+class GitExporter(object):
+    """An exporter for testgit repositories.
+
+    The exporter simply delegates to git fast-export.
+    """
+
+    def __init__(self, repo):
+        """Creates a new exporter for the specified repo.
+        """
+
+        self.repo = repo
+
+    def export_repo(self, base):
+        """Exports a fast-export stream for the given directory.
+
+        Simply delegates to git fast-epxort and pipes it through sed
+        to make the refs show up under the prefix rather than the
+        default refs/heads. This is to demonstrate how the export
+        data can be stored under it's own ref (using the refspec
+        capability).
+        """
+
+        dirname = self.repo.get_base_path(base)
+        path = os.path.abspath(os.path.join(dirname, 'testgit.marks'))
+
+        if not os.path.exists(dirname):
+            os.makedirs(dirname)
+
+        print "feature relative-marks"
+        if os.path.exists(os.path.join(dirname, 'git.marks')):
+            print "feature import-marks=%s/git.marks" % self.repo.hash
+        print "feature export-marks=%s/git.marks" % self.repo.hash
+        sys.stdout.flush()
+
+        args = ["git", "--git-dir=" + self.repo.gitpath, "fast-export", "--export-marks=" + path]
+
+        if os.path.exists(path):
+            args.append("--import-marks=" + path)
+
+        args.append("HEAD")
+
+        p1 = subprocess.Popen(args, stdout=subprocess.PIPE)
+
+        args = ["sed", "s_refs/heads/_" + self.repo.prefix + "_g"]
+
+        subprocess.check_call(args, stdin=p1.stdout)
diff --git a/git_remote_helpers/git/importer.py b/git_remote_helpers/git/importer.py
new file mode 100644
index 0000000000..af2919d92c
--- /dev/null
+++ b/git_remote_helpers/git/importer.py
@@ -0,0 +1,38 @@
+import os
+import subprocess
+
+
+class GitImporter(object):
+    """An importer for testgit repositories.
+
+    This importer simply delegates to git fast-import.
+    """
+
+    def __init__(self, repo):
+        """Creates a new importer for the specified repo.
+        """
+
+        self.repo = repo
+
+    def do_import(self, base):
+        """Imports a fast-import stream to the given directory.
+
+        Simply delegates to git fast-import.
+        """
+
+        dirname = self.repo.get_base_path(base)
+        if self.repo.local:
+            gitdir = self.repo.gitpath
+        else:
+            gitdir = os.path.abspath(os.path.join(dirname, '.git'))
+        path = os.path.abspath(os.path.join(dirname, 'git.marks'))
+
+        if not os.path.exists(dirname):
+            os.makedirs(dirname)
+
+        args = ["git", "--git-dir=" + gitdir, "fast-import", "--quiet", "--export-marks=" + path]
+
+        if os.path.exists(path):
+            args.append("--import-marks=" + path)
+
+        subprocess.check_call(args)
diff --git a/git_remote_helpers/git/non_local.py b/git_remote_helpers/git/non_local.py
new file mode 100644
index 0000000000..d75ef8f214
--- /dev/null
+++ b/git_remote_helpers/git/non_local.py
@@ -0,0 +1,61 @@
+import os
+import subprocess
+
+from git_remote_helpers.util import die, warn
+
+
+class NonLocalGit(object):
+    """Handler to interact with non-local repos.
+    """
+
+    def __init__(self, repo):
+        """Creates a new non-local handler for the specified repo.
+        """
+
+        self.repo = repo
+
+    def clone(self, base):
+        """Clones the non-local repo to base.
+
+        Does nothing if a clone already exists.
+        """
+
+        path = os.path.join(self.repo.get_base_path(base), '.git')
+
+        # already cloned
+        if os.path.exists(path):
+            return path
+
+        os.makedirs(path)
+        args = ["git", "clone", "--bare", "--quiet", self.repo.gitpath, path]
+
+        subprocess.check_call(args)
+
+        return path
+
+    def update(self, base):
+        """Updates checkout of the non-local repo in base.
+        """
+
+        path = os.path.join(self.repo.get_base_path(base), '.git')
+
+        if not os.path.exists(path):
+            die("could not find repo at %s", path)
+
+        args = ["git", "--git-dir=" + path, "fetch", "--quiet", self.repo.gitpath]
+        subprocess.check_call(args)
+
+        args = ["git", "--git-dir=" + path, "update-ref", "refs/heads/master", "FETCH_HEAD"]
+        subprocess.check_call(args)
+
+    def push(self, base):
+        """Pushes from the non-local repo to base.
+        """
+
+        path = os.path.join(self.repo.get_base_path(base), '.git')
+
+        if not os.path.exists(path):
+            die("could not find repo at %s", path)
+
+        args = ["git", "--git-dir=" + path, "push", "--quiet", self.repo.gitpath]
+        subprocess.check_call(args)
diff --git a/git_remote_helpers/git/repo.py b/git_remote_helpers/git/repo.py
new file mode 100644
index 0000000000..82d5f78c7e
--- /dev/null
+++ b/git_remote_helpers/git/repo.py
@@ -0,0 +1,70 @@
+import os
+import subprocess
+
+def sanitize(rev, sep='\t'):
+    """Converts a for-each-ref line to a name/value pair.
+    """
+
+    splitrev = rev.split(sep)
+    branchval = splitrev[0]
+    branchname = splitrev[1].strip()
+    if branchname.startswith("refs/heads/"):
+        branchname = branchname[11:]
+
+    return branchname, branchval
+
+def is_remote(url):
+    """Checks whether the specified value is a remote url.
+    """
+
+    prefixes = ["http", "file", "git"]
+
+    return any(url.startswith(i) for i in prefixes)
+
+class GitRepo(object):
+    """Repo object representing a repo.
+    """
+
+    def __init__(self, path):
+        """Initializes a new repo at the given path.
+        """
+
+        self.path = path
+        self.head = None
+        self.revmap = {}
+        self.local = not is_remote(self.path)
+
+        if(self.path.endswith('.git')):
+            self.gitpath = self.path
+        else:
+            self.gitpath = os.path.join(self.path, '.git')
+
+        if self.local and not os.path.exists(self.gitpath):
+            os.makedirs(self.gitpath)
+
+    def get_revs(self):
+        """Fetches all revs from the remote.
+        """
+
+        args = ["git", "ls-remote", self.gitpath]
+        path = ".cached_revs"
+        ofile = open(path, "w")
+
+        subprocess.check_call(args, stdout=ofile)
+        output = open(path).readlines()
+        self.revmap = dict(sanitize(i) for i in output)
+        if "HEAD" in self.revmap:
+            del self.revmap["HEAD"]
+        self.revs = self.revmap.keys()
+        ofile.close()
+
+    def get_head(self):
+        """Determines the head of a local repo.
+        """
+
+        if not self.local:
+            return
+
+        path = os.path.join(self.gitpath, "HEAD")
+        head = open(path).readline()
+        self.head, _ = sanitize(head, ' ')