Bug 1279563 - Offer to clone Firefox source repo during bootstrap; r=glandium

I've always been bothered that the one-line bootstrap configures your system
then leaves you on the hook to clone source code and configure the build
system. I'd like the bootstrap wizard to guide you through end-to-end.

This commit addresses part of the disconnect by offering to clone the
Mercurial source repository at the end of bootstrap.

We only offer to clone if we aren't running from a Firefox source checkout
(likely the one-line bootstrap invocation) and if we are in interactive
mode.

I'd like to eventually offer Git support here. Mercurial is the canonical
repo, so it makes sense to start with that.

MozReview-Commit-ID: 6TSZwxB3702

--HG--
extra : rebase_source : 5c35408a4f0e59d681ca28e5b23359c54927b513
extra : amend_source : f980b972e35a17e733e704e47efdd773b3633e45

python/mozboot/mozboot/bootstrap.py

@@ -82,8 +82,11 @@ Your choice:
 '''
 
 FINISHED = '''
-Your system should be ready to build %s! If you have not already,
-obtain a copy of the source code by running:
+Your system should be ready to build %s!
+'''
+
+SOURCE_ADVERTISE = '''
+Source code can be obtained by running
 
     hg clone https://hg.mozilla.org/mozilla-central
 
@@ -109,6 +112,15 @@ optimally configured?
 
 Please enter your reply: '''.lstrip()
 
+CLONE_MERCURIAL = '''
+If you would like to clone the canonical Mercurial repository, please
+enter the destination path below.
+
+(If you prefer to use Git, leave this blank.)
+
+Destination directory for Mercurial clone (leave empty to not clone): '''.lstrip()
+
+
 DEBIAN_DISTROS = (
     'Debian',
     'debian',
@@ -248,6 +260,23 @@ class Bootstrapper(object):
             if configure_hg:
                 configure_mercurial(self.instance.which('hg'), state_dir)
 
+        # Offer to clone if we're not inside a clone.
+        checkout_type = current_firefox_checkout(check_output=self.instance.check_output,
+                                                 hg=self.instance.which('hg'))
+        have_clone = False
+
+        if checkout_type:
+            have_clone = True
+        elif hg_installed and not self.instance.no_interactive:
+            dest = raw_input(CLONE_MERCURIAL)
+            dest = dest.strip()
+            if dest:
+                dest = os.path.expanduser(dest)
+                have_clone = clone_firefox(self.instance.which('hg'), dest)
+
+        if not have_clone:
+            print(SOURCE_ADVERTISE)
+
         print(self.finished % name)
 
         # Like 'suggest_browser_mozconfig' or 'suggest_mobile_android_mozconfig'.
@@ -313,3 +342,61 @@ def update_mercurial_repo(hg, url, dest, revision):
         subprocess.check_call([hg, 'update', '-r', revision], cwd=dest)
     finally:
         print('=' * 80)
+
+
+def clone_firefox(hg, dest):
+    """Clone the Firefox repository to a specified destination."""
+    print('Cloning Firefox Mercurial repository to %s' % dest)
+
+    args = [
+        hg,
+        'clone',
+        'https://hg.mozilla.org/mozilla-central',
+        dest,
+    ]
+
+    res = subprocess.call(args)
+    print('')
+    if res:
+        print('error cloning; please try again')
+        return False
+    else:
+        print('Firefox source code available at %s' % dest)
+        return True
+
+
+def current_firefox_checkout(check_output, hg=None):
+    """Determine whether we're in a Firefox checkout.
+
+    Returns one of None, ``git``, or ``hg``.
+    """
+    HG_ROOT_REVISIONS = set([
+        # From mozilla-central.
+        '8ba995b74e18334ab3707f27e9eb8f4e37ba3d29',
+    ])
+
+    path = os.getcwd()
+    while path:
+        hg_dir = os.path.join(path, '.hg')
+        git_dir = os.path.join(path, '.git')
+        if hg and os.path.exists(hg_dir):
+            # Verify the hg repo is a Firefox repo by looking at rev 0.
+            try:
+                node = check_output([hg, 'log', '-r', '0', '-T', '{node}'], cwd=path)
+                if node in HG_ROOT_REVISIONS:
+                    return 'hg'
+                # Else the root revision is different. There could be nested
+                # repos. So keep traversing the parents.
+            except subprocess.CalledProcessError:
+                pass
+
+        # TODO check git remotes or `git rev-parse -q --verify $sha1^{commit}`
+        # for signs of Firefox.
+        elif os.path.exists(git_dir):
+            return 'git'
+
+        path, child = os.path.split(path)
+        if child == '':
+            break
+
+    return None