repo: Add support for standalone manifests

Added --standalone_manifest to repo tool. If set, the
manifest is downloaded directly from the appropriate source
(currently, we only support GS) and used instead of creating
a manifest git checkout. The manifests.git repo is still created to
keep track of various config but is marked as being for a standalone
manifest so that the repo tool doesn't try to run networked git
commands in it.

BUG=b:192664812
TEST=existing tests (no coverage), manual runs

Change-Id: I84378cbc7f8e515eabeccdde9665efc8cd2a9d21
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/312942
Tested-by: Jack Neus <jackneus@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>

7 files changed, 132 insertions, 18 deletions

diff --git a/docs/internal-fs-layout.md b/docs/internal-fs-layout.md
index e3be1731..af6a4523 100644
--- a/docs/internal-fs-layout.md
+++ b/docs/internal-fs-layout.md
@@ -157,6 +157,7 @@ User controlled settings are initialized when running `repo init`.
 | Setting                  | `repo init` Option        | Use/Meaning |
 |-------------------       |---------------------------|-------------|
 | manifest.groups          | `--groups` & `--platform` | The manifest groups to sync |
+| manifest.standalone      | `--standalone-manifest`   | Download manifest as static file instead of creating checkout |
 | repo.archive             | `--archive`               | Use `git archive` for checkouts |
 | repo.clonebundle         | `--clone-bundle`          | Whether the initial sync used clone.bundle explicitly |
 | repo.clonefilter         | `--clone-filter`          | Filter setting when using [partial git clones] |
diff --git a/fetch.py b/fetch.py
new file mode 100644
index 00000000..5b9997a8
--- /dev/null
+++ b/fetch.py
@@ -0,0 +1,38 @@
+# Copyright (C) 2021 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""This module contains functions used to fetch files from various sources."""
+
+import subprocess
+import sys
+from urllib.parse import urlparse
+
+def fetch_file(url):
+  """Fetch a file from the specified source using the appropriate protocol.
+
+  Returns:
+    The contents of the file as bytes.
+  """
+  scheme = urlparse(url).scheme
+  if scheme == 'gs':
+    cmd = ['gsutil', 'cat', url]
+    try:
+      result = subprocess.run(
+          cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+      return result.stdout
+    except subprocess.CalledProcessError as e:
+      print('fatal: error running "gsutil": %s' % e.output,
+            file=sys.stderr)
+    sys.exit(1)
+  raise ValueError('unsupported url %s' % url)
diff --git a/git_config.py b/git_config.py
index d882239b..778e81a4 100644
--- a/git_config.py
+++ b/git_config.py
@@ -104,6 +104,10 @@ class GitConfig(object):
           os.path.dirname(self.file),
           '.repo_' + os.path.basename(self.file) + '.json')
 
+  def ClearCache(self):
+    """Clear the in-memory cache of config."""
+    self._cache_dict = None
+
   def Has(self, name, include_defaults=True):
     """Return true if this configuration file has the key.
     """
@@ -399,7 +403,7 @@ class GitConfig(object):
     if p.Wait() == 0:
       return p.stdout
     else:
-      GitError('git config %s: %s' % (str(args), p.stderr))
+      raise GitError('git config %s: %s' % (str(args), p.stderr))
 
 
 class RepoConfig(GitConfig):
diff --git a/man/repo-gitc-init.1 b/man/repo-gitc-init.1
index 1d1b23a8..9b61866e 100644
--- a/man/repo-gitc-init.1
+++ b/man/repo-gitc-init.1
@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man.
-.TH REPO "1" "July 2021" "repo gitc-init" "Repo Manual"
+.TH REPO "1" "September 2021" "repo gitc-init" "Repo Manual"
 .SH NAME
 repo \- repo gitc-init - manual page for repo gitc-init
 .SH SYNOPSIS
@@ -31,6 +31,10 @@ manifest branch or revision (use HEAD for default)
 \fB\-m\fR NAME.xml, \fB\-\-manifest\-name\fR=\fI\,NAME\/\fR.xml
 initial manifest file
 .TP
+\fB\-\-standalone\-manifest\fR
+download the manifest as a static file rather then
+create a git checkout of the manifest repo
+.TP
 \fB\-g\fR GROUP, \fB\-\-groups\fR=\fI\,GROUP\/\fR
 restrict manifest projects to ones with specified
 group(s) [default|all|G1,G2,G3|G4,\-G5,\-G6]
diff --git a/man/repo-init.1 b/man/repo-init.1
index e860f95d..9957b64d 100644
--- a/man/repo-init.1
+++ b/man/repo-init.1
@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man.
-.TH REPO "1" "July 2021" "repo init" "Repo Manual"
+.TH REPO "1" "September 2021" "repo init" "Repo Manual"
 .SH NAME
 repo \- repo init - manual page for repo init
 .SH SYNOPSIS
@@ -31,6 +31,10 @@ manifest branch or revision (use HEAD for default)
 \fB\-m\fR NAME.xml, \fB\-\-manifest\-name\fR=\fI\,NAME\/\fR.xml
 initial manifest file
 .TP
+\fB\-\-standalone\-manifest\fR
+download the manifest as a static file rather then
+create a git checkout of the manifest repo
+.TP
 \fB\-g\fR GROUP, \fB\-\-groups\fR=\fI\,GROUP\/\fR
 restrict manifest projects to ones with specified
 group(s) [default|all|G1,G2,G3|G4,\-G5,\-G6]
@@ -137,6 +141,12 @@ equivalent to using \fB\-b\fR HEAD.
 The optional \fB\-m\fR argument can be used to specify an alternate manifest to be
 used. If no manifest is specified, the manifest default.xml will be used.
 .PP
+If the \fB\-\-standalone\-manifest\fR argument is set, the manifest will be downloaded
+directly from the specified \fB\-\-manifest\-url\fR as a static file (rather than setting
+up a manifest git checkout). With \fB\-\-standalone\-manifest\fR, the manifest will be
+fully static and will not be re\-downloaded during subsesquent `repo init` and
+`repo sync` calls.
+.PP
 The \fB\-\-reference\fR option can be used to point to a directory that has the content
 of a \fB\-\-mirror\fR sync. This will make the working directory use as much data as
 possible from the local reference directory when fetching from the server. This
diff --git a/repo b/repo
index 3b244c16..f61639f3 100755
--- a/repo
+++ b/repo
@@ -312,6 +312,10 @@ def InitParser(parser, gitc_init=False):
                    metavar='PLATFORM')
   group.add_option('--submodules', action='store_true',
                    help='sync any submodules associated with the manifest repo')
+  group.add_option('--standalone-manifest', action='store_true',
+                   help='download the manifest as a static file '
+                        'rather then create a git checkout of '
+                        'the manifest repo')
 
   # Options that only affect manifest project, and not any of the projects
   # specified in the manifest itself.
diff --git a/subcmds/init.py b/subcmds/init.py
index 5671fc24..9c6b2ad9 100644
--- a/subcmds/init.py
+++ b/subcmds/init.py
@@ -15,6 +15,7 @@
 import os
 import platform
 import re
+import subprocess
 import sys
 import urllib.parse
 
@@ -24,6 +25,7 @@ from error import ManifestParseError
 from project import SyncBuffer
 from git_config import GitConfig
 from git_command import git_require, MIN_GIT_VERSION_SOFT, MIN_GIT_VERSION_HARD
+import fetch
 import git_superproject
 import platform_utils
 from wrapper import Wrapper
@@ -53,6 +55,12 @@ The optional -m argument can be used to specify an alternate manifest
 to be used. If no manifest is specified, the manifest default.xml
 will be used.
 
+If the --standalone-manifest argument is set, the manifest will be downloaded
+directly from the specified --manifest-url as a static file (rather than
+setting up a manifest git checkout). With --standalone-manifest, the manifest
+will be fully static and will not be re-downloaded during subsesquent
+`repo init` and `repo sync` calls.
+
 The --reference option can be used to point to a directory that
 has the content of a --mirror sync. This will make the working
 directory use as much data as possible from the local reference
@@ -112,6 +120,22 @@ to update the working directory files.
     m = self.manifest.manifestProject
     is_new = not m.Exists
 
+    # If repo has already been initialized, we take -u with the absence of
+    # --standalone-manifest to mean "transition to a standard repo set up",
+    # which necessitates starting fresh.
+    # If --standalone-manifest is set, we always tear everything down and start
+    # anew.
+    if not is_new:
+      was_standalone_manifest = m.config.GetString('manifest.standalone')
+      if opt.standalone_manifest or (
+          was_standalone_manifest and opt.manifest_url):
+        m.config.ClearCache()
+        if m.gitdir and os.path.exists(m.gitdir):
+          platform_utils.rmtree(m.gitdir)
+        if m.worktree and os.path.exists(m.worktree):
+          platform_utils.rmtree(m.worktree)
+
+    is_new = not m.Exists
     if is_new:
       if not opt.manifest_url:
         print('fatal: manifest url is required.', file=sys.stderr)
@@ -136,6 +160,19 @@ to update the working directory files.
 
       m._InitGitDir(mirror_git=mirrored_manifest_git)
 
+    # If standalone_manifest is set, mark the project as "standalone" -- we'll
+    # still do much of the manifests.git set up, but will avoid actual syncs to
+    # a remote.
+    standalone_manifest = False
+    if opt.standalone_manifest:
+      standalone_manifest = True
+    elif not opt.manifest_url:
+      # If -u is set and --standalone-manifest is not, then we're not in
+      # standalone mode. Otherwise, use config to infer what we were in the last
+      # init.
+      standalone_manifest = bool(m.config.GetString('manifest.standalone'))
+    m.config.SetString('manifest.standalone', opt.manifest_url)
+
     self._ConfigureDepth(opt)
 
     # Set the remote URL before the remote branch as we might need it below.
@@ -145,22 +182,23 @@ to update the working directory files.
       r.ResetFetch()
       r.Save()
 
-    if opt.manifest_branch:
-      if opt.manifest_branch == 'HEAD':
-        opt.manifest_branch = m.ResolveRemoteHead()
-        if opt.manifest_branch is None:
-          print('fatal: unable to resolve HEAD', file=sys.stderr)
-          sys.exit(1)
-      m.revisionExpr = opt.manifest_branch
-    else:
-      if is_new:
-        default_branch = m.ResolveRemoteHead()
-        if default_branch is None:
-          # If the remote doesn't have HEAD configured, default to master.
-          default_branch = 'refs/heads/master'
-        m.revisionExpr = default_branch
+    if not standalone_manifest:
+      if opt.manifest_branch:
+        if opt.manifest_branch == 'HEAD':
+          opt.manifest_branch = m.ResolveRemoteHead()
+          if opt.manifest_branch is None:
+            print('fatal: unable to resolve HEAD', file=sys.stderr)
+            sys.exit(1)
+        m.revisionExpr = opt.manifest_branch
       else:
-        m.PreSync()
+        if is_new:
+          default_branch = m.ResolveRemoteHead()
+          if default_branch is None:
+            # If the remote doesn't have HEAD configured, default to master.
+            default_branch = 'refs/heads/master'
+          m.revisionExpr = default_branch
+        else:
+          m.PreSync()
 
     groups = re.split(r'[,\s]+', opt.groups)
     all_platforms = ['linux', 'darwin', 'windows']
@@ -250,6 +288,16 @@ to update the working directory files.
     if opt.use_superproject is not None:
       m.config.SetBoolean('repo.superproject', opt.use_superproject)
 
+    if standalone_manifest:
+      if is_new:
+        manifest_name = 'default.xml'
+        manifest_data = fetch.fetch_file(opt.manifest_url)
+        dest = os.path.join(m.worktree, manifest_name)
+        os.makedirs(os.path.dirname(dest), exist_ok=True)
+        with open(dest, 'wb') as f:
+          f.write(manifest_data)
+      return
+
     if not m.Sync_NetworkHalf(is_new=is_new, quiet=opt.quiet, verbose=opt.verbose,
                               clone_bundle=opt.clone_bundle,
                               current_branch_only=opt.current_branch_only,
@@ -426,6 +474,11 @@ to update the working directory files.
     if opt.archive and opt.mirror:
       self.OptionParser.error('--mirror and --archive cannot be used together.')
 
+    if opt.standalone_manifest and (
+        opt.manifest_branch or opt.manifest_name != 'default.xml'):
+      self.OptionParser.error('--manifest-branch and --manifest-name cannot'
+                              ' be used with --standalone-manifest.')
+
     if args:
       if opt.manifest_url:
         self.OptionParser.error(