gc: Add tags to remote pack list

If tags are omitted from the remote pack list, they must be present in
local pack. However, local packs don't have promisor objects, meaning
that all blobs must be available locally, and therefore all missing
blobs will be downloaded during rev-list phase. Git downloads those
sequentially, by invokving fetch operation (rev-list/fetch).

Instead of downloading tags' blobs, instruct Git to include all tags in
remote rev-list operation. This change was tested with `git fsck --all`.

R=yiwzhang@google.com

Bug: b/392732561
Change-Id: Id94a40aebbe4f084c952329583d559d296db1a11
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/451422
Reviewed-by: Yiwei Zhang <yiwzhang@google.com>
Tested-by: Josip Sokcevic <sokcevic@chromium.org>
Commit-Queue: Josip Sokcevic <sokcevic@chromium.org>

docs/internal-fs-layout.md

@@ -141,7 +141,7 @@ Instead, you should use standard Git workflows like [git worktree] or
     (e.g. a local mirror & a public review server) while avoiding duplicating
     the content.  However, this can run into problems if different remotes use
     the same path on their respective servers.  Best to avoid that.
-*   `subprojects/`: Like `projects/`, but for git submodules.
+*   `modules/`: Like `projects/`, but for git submodules.
 *   `subproject-objects/`: Like `project-objects/`, but for git submodules.
 *   `worktrees/`: Bare checkouts of every project synced by the manifest.  The
     filesystem layout matches the `<project name=...` setting in the manifest

docs/manifest-format.md

@@ -231,26 +231,7 @@ At most one manifest-server may be specified. The url attribute
 is used to specify the URL of a manifest server, which is an
 XML RPC service.
 
-The manifest server should implement the following RPC methods:
+See the [smart sync documentation](./smart-sync.md) for more details.
-
-    GetApprovedManifest(branch, target)
-
-Return a manifest in which each project is pegged to a known good revision
-for the current branch and target. This is used by repo sync when the
---smart-sync option is given.
-
-The target to use is defined by environment variables TARGET_PRODUCT
-and TARGET_BUILD_VARIANT. These variables are used to create a string
-of the form $TARGET_PRODUCT-$TARGET_BUILD_VARIANT, e.g. passion-userdebug.
-If one of those variables or both are not present, the program will call
-GetApprovedManifest without the target parameter and the manifest server
-should choose a reasonable default target.
-
-    GetManifest(tag)
-
-Return a manifest in which each project is pegged to the revision at
-the specified tag. This is used by repo sync when the --smart-tag option
-is given.
 
 
 ### Element submanifest

docs/smart-sync.md

@@ -0,0 +1,129 @@
+# repo Smart Syncing
+
+Repo normally fetches & syncs manifests from the same URL specified during
+`repo init`, and that often fetches the latest revisions of all projects in
+the manifest.  This flow works well for tracking and developing with the
+latest code, but often it's desirable to sync to other points.  For example,
+to get a local build matching a specific release or build to reproduce bugs
+reported by other people.
+
+Repo's sync subcommand has support for fetching manifests from a server over
+an XML-RPC connection.  The local configuration and network API are defined by
+repo, but individual projects have to host their own server for the client to
+communicate with.
+
+This process is called "smart syncing" -- instead of blindly fetching the latest
+revision of all projects and getting an unknown state to develop against, the
+client passes a request to the server and is given a matching manifest that
+typically specifies specific commits for every project to fetch a known source
+state.
+
+[TOC]
+
+## Manifest Configuration
+
+The manifest specifies the server to communicate with via the
+the [`<manifest-server>` element](manifest-format.md#Element-manifest_server)
+element.  This is how the client knows what service to talk to.
+
+```xml
+  <manifest-server url="https://example.com/your/manifest/server/url" />
+```
+
+If the URL starts with `persistent-`, then the
+[`git-remote-persistent-https` helper](https://github.com/git/git/blob/HEAD/contrib/persistent-https/README)
+is used to communicate with the server.
+
+## Credentials
+
+Credentials may be specified directly in typical `username:password`
+[URI syntax](https://en.wikipedia.org/wiki/URI#Syntax) in the
+`<manifest-server>` element directly in the manifest.
+
+If they are not specified, `repo sync` has `--manifest-server-username=USERNAME`
+and `--manifest-server-password=PASSWORD` options.
+
+If those are not used, then repo will look up the host in your
+[`~/.netrc`](https://docs.python.org/3/library/netrc.html) database.
+
+When making the connection, cookies matching the host are automatically loaded
+from the cookiejar specified in
+[Git's `http.cookiefile` setting](https://git-scm.com/docs/git-config#Documentation/git-config.txt-httpcookieFile).
+
+## Manifest Server
+
+Unfortunately, there are no public reference implementations.  Google has an
+internal one for Android, but it is written using Google's internal systems,
+so wouldn't be that helpful as a reference.
+
+That said, the XML-RPC API is pretty simple, so any standard XML-RPC server
+example would do.  Google's internal server uses Python's
+[xmlrpc.server.SimpleXMLRPCDispatcher](https://docs.python.org/3/library/xmlrpc.server.html).
+
+## Network API
+
+The manifest server should implement the following RPC methods.
+
+### GetApprovedManifest
+
+> `GetApprovedManifest(branch: str, target: Optional[str]) -> str`
+
+The meaning of `branch` and `target` is not strictly defined.  The server may
+interpret them however it wants.  The recommended interpretation is that the
+`branch` matches the manifest branch, and `target` is an identifier for your
+project that matches something users would build.
+
+See the client section below for how repo typically generates these values.
+
+The server will return a manifest or an error.  If it's an error, repo will
+show the output directly to the user to provide a limited feedback channel.
+
+If the user's request is ambiguous and could match multiple manifests, the
+server has to decide whether to pick one automatically (and silently such that
+the user won't know there were multiple matches), or return an error and force
+the user to be more specific.
+
+### GetManifest
+
+> `GetManifest(tag: str) -> str`
+
+The meaning of `tag` is not strictly defined.  Projects are encouraged to use
+a system where the tag matches a unique source state.
+
+See the client section below for how repo typically generates these values.
+
+The server will return a manifest or an error.  If it's an error, repo will
+show the output directly to the user to provide a limited feedback channel.
+
+If the user's request is ambiguous and could match multiple manifests, the
+server has to decide whether to pick one automatically (and silently such that
+the user won't know there were multiple matches), or return an error and force
+the user to be more specific.
+
+## Client Options
+
+Once repo has successfully downloaded the manifest from the server, it saves a
+copy into `.repo/manifests/smart_sync_override.xml` so users can examine it.
+The next time `repo sync` is run, this file is automatically replaced or removed
+based on the current set of options.
+
+### --smart-sync
+
+Repo will call `GetApprovedManifest(branch[, target])`.
+
+The `branch` is determined by the current manifest branch as specified by
+`--manifest-branch=BRANCH` when running `repo init`.
+
+The `target` is defined by environment variables in the order below.  If none
+of them match, then `target` is omitted.  These variables were decided as they
+match the settings Android build environments automatically setup.
+
+1.  `${SYNC_TARGET}`: If defined, the value is used directly.
+2.  `${TARGET_PRODUCT}-${TARGET_RELEASE}-${TARGET_BUILD_VARIANT}`: If these
+    variables are all defined, then they are merged with `-` and used.
+3.  `${TARGET_PRODUCT}-${TARGET_BUILD_VARIANT}`: If these variables are all
+    defined, then they are merged with `-` and used.
+
+### --smart-tag=TAG
+
+Repo will call `GetManifest(TAG)`.

git_config.py

@@ -90,6 +90,20 @@ class GitConfig:
 
     @staticmethod
     def _getUserConfig():
+        """Get the user-specific config file.
+
+        Prefers the XDG config location if available, with fallback to
+        ~/.gitconfig
+
+        This matches git behavior:
+        https://git-scm.com/docs/git-config#FILES
+        """
+        xdg_config_home = os.getenv(
+            "XDG_CONFIG_HOME", os.path.expanduser("~/.config")
+        )
+        xdg_config_file = os.path.join(xdg_config_home, "git", "config")
+        if os.path.exists(xdg_config_file):
+            return xdg_config_file
         return os.path.expanduser("~/.gitconfig")
 
     @classmethod

man/repo-gc.1

@@ -0,0 +1,43 @@
+.\" DO NOT MODIFY THIS FILE!  It was generated by help2man.
+.TH REPO "1" "December 2024" "repo gc" "Repo Manual"
+.SH NAME
+repo \- repo gc - manual page for repo gc
+.SH SYNOPSIS
+.B repo
+\fI\,gc\/\fR
+.SH DESCRIPTION
+Summary
+.PP
+Cleaning up internal repo state.
+.SH OPTIONS
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+show this help message and exit
+.TP
+\fB\-n\fR, \fB\-\-dry\-run\fR
+do everything except actually delete
+.TP
+\fB\-y\fR, \fB\-\-yes\fR
+answer yes to all safe prompts
+.SS Logging options:
+.TP
+\fB\-v\fR, \fB\-\-verbose\fR
+show all output
+.TP
+\fB\-q\fR, \fB\-\-quiet\fR
+only show errors
+.SS Multi\-manifest options:
+.TP
+\fB\-\-outer\-manifest\fR
+operate starting at the outermost manifest
+.TP
+\fB\-\-no\-outer\-manifest\fR
+do not operate on outer manifests
+.TP
+\fB\-\-this\-manifest\-only\fR
+only operate on this (sub)manifest
+.TP
+\fB\-\-no\-this\-manifest\-only\fR, \fB\-\-all\-manifests\fR
+operate on this manifest and its submanifests
+.PP
+Run `repo help gc` to view the detailed manual.

man/repo-manifest.1

@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man.
-.TH REPO "1" "April 2024" "repo manifest" "Repo Manual"
+.TH REPO "1" "December 2024" "repo manifest" "Repo Manual"
 .SH NAME
 repo \- repo manifest - manual page for repo manifest
 .SH SYNOPSIS
@@ -192,11 +192,13 @@ CDATA #IMPLIED>
 <!ATTLIST extend\-project remote CDATA #IMPLIED>
 <!ATTLIST extend\-project dest\-branch CDATA #IMPLIED>
 <!ATTLIST extend\-project upstream CDATA #IMPLIED>
+<!ATTLIST extend\-project base\-rev CDATA #IMPLIED>
 .IP
 <!ELEMENT remove\-project EMPTY>
 <!ATTLIST remove\-project name     CDATA #IMPLIED>
 <!ATTLIST remove\-project path     CDATA #IMPLIED>
 <!ATTLIST remove\-project optional CDATA #IMPLIED>
+<!ATTLIST remove\-project base\-rev CDATA #IMPLIED>
 .IP
 <!ELEMENT repo\-hooks EMPTY>
 <!ATTLIST repo\-hooks in\-project CDATA #REQUIRED>
@@ -495,6 +497,14 @@ project. Same syntax as the corresponding element of `project`.
 Attribute `upstream`: If specified, overrides the upstream of the original
 project. Same syntax as the corresponding element of `project`.
 .PP
+Attribute `base\-rev`: If specified, adds a check against the revision to be
+extended. Manifest parse will fail and give a list of mismatch extends if the
+revisions being extended have changed since base\-rev was set. Intended for use
+with layered manifests using hash revisions to prevent patch branches hiding
+newer upstream revisions. Also compares named refs like branches or tags but is
+misleading if branches are used as base\-rev. Same syntax as the corresponding
+element of `project`.
+.PP
 Element annotation
 .PP
 Zero or more annotation elements may be specified as children of a project or
@@ -556,6 +566,14 @@ Logic otherwise behaves like both are specified.
 Attribute `optional`: Set to true to ignore remove\-project elements with no
 matching `project` element.
 .PP
+Attribute `base\-rev`: If specified, adds a check against the revision to be
+removed. Manifest parse will fail and give a list of mismatch removes if the
+revisions being removed have changed since base\-rev was set. Intended for use
+with layered manifests using hash revisions to prevent patch branches hiding
+newer upstream revisions. Also compares named refs like branches or tags but is
+misleading if branches are used as base\-rev. Same syntax as the corresponding
+element of `project`.
+.PP
 Element repo\-hooks
 .PP
 NB: See the [practical documentation](./repo\-hooks.md) for using repo hooks.

man/repo.1

@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man.
-.TH REPO "1" "April 2024" "repo" "Repo Manual"
+.TH REPO "1" "December 2024" "repo" "Repo Manual"
 .SH NAME
 repo \- repository management tool built on top of git
 .SH SYNOPSIS
@@ -79,6 +79,9 @@ Download and checkout a change
 forall
 Run a shell command in each project
 .TP
+gc
+Cleaning up internal repo state.
+.TP
 grep
 Print lines matching a pattern
 .TP

manifest_xml.py

@@ -2056,7 +2056,12 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
         path = path.rstrip("/")
         name = name.rstrip("/")
         relpath = self._JoinRelpath(parent.relpath, path)
-        gitdir = os.path.join(parent.gitdir, "subprojects", "%s.git" % path)
+        subprojects = os.path.join(parent.gitdir, "subprojects", f"{path}.git")
+        modules = os.path.join(parent.gitdir, "modules", path)
+        if platform_utils.isdir(subprojects):
+            gitdir = subprojects
+        else:
+            gitdir = modules
         objdir = os.path.join(
             parent.gitdir, "subproject-objects", "%s.git" % name
         )

project.py

@@ -642,6 +642,10 @@ class Project:
         # project containing repo hooks.
         self.enabled_repo_hooks = []
 
+        # This will be updated later if the project has submodules and
+        # if they will be synced.
+        self.has_subprojects = False
+
     def RelPath(self, local=True):
         """Return the path for the project relative to a manifest.
 
@@ -1560,6 +1564,11 @@ class Project:
             return
 
         self._InitWorkTree(force_sync=force_sync, submodules=submodules)
+        # TODO(https://git-scm.com/docs/git-worktree#_bugs): Re-evaluate if
+        # submodules can be init when using worktrees once its support is
+        # complete.
+        if self.has_subprojects and not self.use_git_worktrees:
+            self._InitSubmodules()
         all_refs = self.bare_ref.all
         self.CleanPublishedCache(all_refs)
         revid = self.GetRevisionId(all_refs)
@@ -2347,6 +2356,8 @@ class Project:
             )
             result.append(subproject)
             result.extend(subproject.GetDerivedSubprojects())
+        if result:
+            self.has_subprojects = True
         return result
 
     def EnableRepositoryExtension(self, key, value="true", version=1):
@@ -2997,6 +3008,17 @@ class Project:
                 project=self.name,
             )
 
+    def _InitSubmodules(self, quiet=True):
+        """Initialize the submodules for the project."""
+        cmd = ["submodule", "init"]
+        if quiet:
+            cmd.append("-q")
+        if GitCommand(self, cmd).Wait() != 0:
+            raise GitError(
+                f"{self.name} submodule init",
+                project=self.name,
+            )
+
     def _Rebase(self, upstream, onto=None):
         cmd = ["rebase"]
         if onto is not None:
@@ -3415,6 +3437,11 @@ class Project:
         """
         dotgit = os.path.join(self.worktree, ".git")
 
+        # If bare checkout of the submodule is stored under the subproject dir,
+        # migrate it.
+        if self.parent:
+            self._MigrateOldSubmoduleDir()
+
         # If using an old layout style (a directory), migrate it.
         if not platform_utils.islink(dotgit) and platform_utils.isdir(dotgit):
             self._MigrateOldWorkTreeGitDir(dotgit, project=self.name)
@@ -3425,34 +3452,76 @@ class Project:
                 self._InitGitWorktree()
                 self._CopyAndLinkFiles()
         else:
+            # Remove old directory symbolic links for submodules.
+            if self.parent and platform_utils.islink(dotgit):
+                platform_utils.remove(dotgit)
+                init_dotgit = True
+
             if not init_dotgit:
                 # See if the project has changed.
-                if os.path.realpath(self.gitdir) != os.path.realpath(dotgit):
+                self._removeBadGitDirLink(dotgit)
-                    platform_utils.remove(dotgit)
 
             if init_dotgit or not os.path.exists(dotgit):
-                os.makedirs(self.worktree, exist_ok=True)
+                self._createDotGit(dotgit)
-                platform_utils.symlink(
-                    os.path.relpath(self.gitdir, self.worktree), dotgit
-                )
 
             if init_dotgit:
                 _lwrite(
-                    os.path.join(dotgit, HEAD), "%s\n" % self.GetRevisionId()
+                    os.path.join(self.gitdir, HEAD), f"{self.GetRevisionId()}\n"
                 )
 
                 # Finish checking out the worktree.
                 cmd = ["read-tree", "--reset", "-u", "-v", HEAD]
-                if GitCommand(self, cmd).Wait() != 0:
+                try:
-                    raise GitError(
+                    if GitCommand(self, cmd).Wait() != 0:
-                        "Cannot initialize work tree for " + self.name,
+                        raise GitError(
-                        project=self.name,
+                            "Cannot initialize work tree for " + self.name,
-                    )
+                            project=self.name,
+                        )
+                except Exception as e:
+                    # Something went wrong with read-tree (perhaps fetching
+                    # missing blobs), so remove .git to avoid half initialized
+                    # workspace from which repo can't recover on its own.
+                    platform_utils.remove(dotgit)
+                    raise e
 
                 if submodules:
                     self._SyncSubmodules(quiet=True)
                 self._CopyAndLinkFiles()
 
+    def _createDotGit(self, dotgit):
+        """Initialize .git path.
+
+        For submodule projects, create a '.git' file using the gitfile
+        mechanism, and for the rest, create a symbolic link.
+        """
+        os.makedirs(self.worktree, exist_ok=True)
+        if self.parent:
+            _lwrite(
+                dotgit,
+                f"gitdir: {os.path.relpath(self.gitdir, self.worktree)}\n",
+            )
+        else:
+            platform_utils.symlink(
+                os.path.relpath(self.gitdir, self.worktree), dotgit
+            )
+
+    def _removeBadGitDirLink(self, dotgit):
+        """Verify .git is initialized correctly, otherwise delete it."""
+        if self.parent and os.path.isfile(dotgit):
+            with open(dotgit) as fp:
+                setting = fp.read()
+            if not setting.startswith("gitdir:"):
+                raise GitError(
+                    f"'.git' in {self.worktree} must start with 'gitdir:'",
+                    project=self.name,
+                )
+            gitdir = setting.split(":", 1)[1].strip()
+            dotgit_path = os.path.normpath(os.path.join(self.worktree, gitdir))
+        else:
+            dotgit_path = os.path.realpath(dotgit)
+        if os.path.realpath(self.gitdir) != dotgit_path:
+            platform_utils.remove(dotgit)
+
     @classmethod
     def _MigrateOldWorkTreeGitDir(cls, dotgit, project=None):
         """Migrate the old worktree .git/ dir style to a symlink.
@@ -3541,6 +3610,28 @@ class Project:
             dotgit,
         )
 
+    def _MigrateOldSubmoduleDir(self):
+        """Move the old bare checkout in 'subprojects' to 'modules'
+        as bare checkouts of submodules are now in 'modules' dir.
+        """
+        subprojects = os.path.join(self.parent.gitdir, "subprojects")
+        if not platform_utils.isdir(subprojects):
+            return
+
+        modules = os.path.join(self.parent.gitdir, "modules")
+        old = self.gitdir
+        new = os.path.splitext(self.gitdir.replace(subprojects, modules))[0]
+
+        if all(map(platform_utils.isdir, [old, new])):
+            platform_utils.rmtree(old, ignore_errors=True)
+        else:
+            os.makedirs(modules, exist_ok=True)
+            platform_utils.rename(old, new)
+        self.gitdir = new
+        self.UpdatePaths(self.relpath, self.worktree, self.gitdir, self.objdir)
+        if platform_utils.isdir(subprojects) and not os.listdir(subprojects):
+            platform_utils.rmtree(subprojects, ignore_errors=True)
+
     def _get_symlink_error_message(self):
         if platform_utils.isWindows():
             return (

run_tests.vpython3

@@ -5,61 +5,55 @@
 # List of available wheels:
 #   https://chromium.googlesource.com/infra/infra/+/main/infra/tools/dockerbuild/wheels.md
 
-python_version: "3.8"
+python_version: "3.11"
 
 wheel: <
   name: "infra/python/wheels/pytest-py3"
-  version: "version:6.2.2"
+  version: "version:8.3.4"
 >
 
-# Required by pytest==6.2.2
+# Required by pytest==8.3.4
 wheel: <
   name: "infra/python/wheels/py-py2_py3"
-  version: "version:1.10.0"
+  version: "version:1.11.0"
 >
 
-# Required by pytest==6.2.2
+# Required by pytest==8.3.4
 wheel: <
   name: "infra/python/wheels/iniconfig-py3"
   version: "version:1.1.1"
 >
 
-# Required by pytest==6.2.2
+# Required by pytest==8.3.4
 wheel: <
   name: "infra/python/wheels/packaging-py3"
   version: "version:23.0"
 >
 
-# Required by pytest==6.2.2
+# Required by pytest==8.3.4
 wheel: <
   name: "infra/python/wheels/pluggy-py3"
-  version: "version:0.13.1"
+  version: "version:1.5.0"
 >
 
-# Required by pytest==6.2.2
+# Required by pytest==8.3.4
 wheel: <
   name: "infra/python/wheels/toml-py3"
   version: "version:0.10.1"
 >
 
-# Required by pytest==6.2.2
+# Required by pytest==8.3.4
 wheel: <
   name: "infra/python/wheels/pyparsing-py3"
   version: "version:3.0.7"
 >
 
-# Required by pytest==6.2.2
+# Required by pytest==8.3.4
 wheel: <
   name: "infra/python/wheels/attrs-py2_py3"
   version: "version:21.4.0"
 >
 
-# Required by packaging==16.8
-wheel: <
-  name: "infra/python/wheels/six-py2_py3"
-  version: "version:1.16.0"
->
-
 wheel: <
   name: "infra/python/wheels/black-py3"
   version: "version:23.1.0"

subcmds/gc.py

@@ -0,0 +1,294 @@
+# Copyright (C) 2024 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.
+
+import os
+from typing import List, Set
+
+from command import Command
+from git_command import GitCommand
+import platform_utils
+from progress import Progress
+from project import Project
+
+
+class Gc(Command):
+    COMMON = True
+    helpSummary = "Cleaning up internal repo and Git state."
+    helpUsage = """
+%prog
+"""
+
+    def _Options(self, p):
+        p.add_option(
+            "-n",
+            "--dry-run",
+            dest="dryrun",
+            default=False,
+            action="store_true",
+            help="do everything except actually delete",
+        )
+        p.add_option(
+            "-y",
+            "--yes",
+            default=False,
+            action="store_true",
+            help="answer yes to all safe prompts",
+        )
+        p.add_option(
+            "--repack",
+            default=False,
+            action="store_true",
+            help="repack all projects that use partial clone with "
+            "filter=blob:none",
+        )
+
+    def _find_git_to_delete(
+        self, to_keep: Set[str], start_dir: str
+    ) -> Set[str]:
+        """Searches no longer needed ".git" directories.
+
+        Scans the file system starting from `start_dir` and removes all
+        directories that end with ".git" that are not in the `to_keep` set.
+        """
+        to_delete = set()
+        for root, dirs, _ in platform_utils.walk(start_dir):
+            for directory in dirs:
+                if not directory.endswith(".git"):
+                    continue
+
+                path = os.path.join(root, directory)
+                if path not in to_keep:
+                    to_delete.add(path)
+
+        return to_delete
+
+    def delete_unused_projects(self, projects: List[Project], opt):
+        print(f"Scanning filesystem under {self.repodir}...")
+
+        project_paths = set()
+        project_object_paths = set()
+
+        for project in projects:
+            project_paths.add(project.gitdir)
+            project_object_paths.add(project.objdir)
+
+        to_delete = self._find_git_to_delete(
+            project_paths, os.path.join(self.repodir, "projects")
+        )
+
+        to_delete.update(
+            self._find_git_to_delete(
+                project_object_paths,
+                os.path.join(self.repodir, "project-objects"),
+            )
+        )
+
+        if not to_delete:
+            print("Nothing to clean up.")
+            return 0
+
+        print("Identified the following projects are no longer used:")
+        print("\n".join(to_delete))
+        print("")
+        if not opt.yes:
+            print(
+                "If you proceed, any local commits in those projects will be "
+                "destroyed!"
+            )
+            ask = input("Proceed? [y/N] ")
+            if ask.lower() != "y":
+                return 1
+
+        pm = Progress(
+            "Deleting",
+            len(to_delete),
+            delay=False,
+            quiet=opt.quiet,
+            show_elapsed=True,
+            elide=True,
+        )
+
+        for path in to_delete:
+            if opt.dryrun:
+                print(f"\nWould have deleted ${path}")
+            else:
+                tmp_path = os.path.join(
+                    os.path.dirname(path),
+                    f"to_be_deleted_{os.path.basename(path)}",
+                )
+                platform_utils.rename(path, tmp_path)
+                platform_utils.rmtree(tmp_path)
+            pm.update(msg=path)
+        pm.end()
+
+        return 0
+
+    def _generate_promisor_files(self, pack_dir: str):
+        """Generates promisor files for all pack files in the given directory.
+
+        Promisor files are empty files with the same name as the corresponding
+        pack file but with the ".promisor" extension. They are used by Git.
+        """
+        for root, _, files in platform_utils.walk(pack_dir):
+            for file in files:
+                if not file.endswith(".pack"):
+                    continue
+                with open(os.path.join(root, f"{file[:-4]}promisor"), "w"):
+                    pass
+
+    def repack_projects(self, projects: List[Project], opt):
+        repack_projects = []
+        # Find all projects eligible for repacking:
+        # - can't be shared
+        # - have a specific fetch filter
+        for project in projects:
+            if project.config.GetBoolean("extensions.preciousObjects"):
+                continue
+            if not project.clone_depth:
+                continue
+            if project.manifest.CloneFilterForDepth != "blob:none":
+                continue
+
+            repack_projects.append(project)
+
+        if opt.dryrun:
+            print(f"Would have repacked {len(repack_projects)} projects.")
+            return 0
+
+        pm = Progress(
+            "Repacking (this will take a while)",
+            len(repack_projects),
+            delay=False,
+            quiet=opt.quiet,
+            show_elapsed=True,
+            elide=True,
+        )
+
+        for project in repack_projects:
+            pm.update(msg=f"{project.name}")
+
+            pack_dir = os.path.join(project.gitdir, "tmp_repo_repack")
+            if os.path.isdir(pack_dir):
+                platform_utils.rmtree(pack_dir)
+            os.mkdir(pack_dir)
+
+            # Prepare workspace for repacking - remove all unreachable refs and
+            # their objects.
+            GitCommand(
+                project,
+                ["reflog", "expire", "--expire-unreachable=all"],
+                verify_command=True,
+            ).Wait()
+            pm.update(msg=f"{project.name} | gc", inc=0)
+            GitCommand(
+                project,
+                ["gc"],
+                verify_command=True,
+            ).Wait()
+
+            # Get all objects that are reachable from the remote, and pack them.
+            pm.update(msg=f"{project.name} | generating list of objects", inc=0)
+            remote_objects_cmd = GitCommand(
+                project,
+                [
+                    "rev-list",
+                    "--objects",
+                    f"--remotes={project.remote.name}",
+                    "--filter=blob:none",
+                    "--tags",
+                ],
+                capture_stdout=True,
+                verify_command=True,
+            )
+
+            # Get all local objects and pack them.
+            local_head_objects_cmd = GitCommand(
+                project,
+                ["rev-list", "--objects", "HEAD^{tree}"],
+                capture_stdout=True,
+                verify_command=True,
+            )
+            local_objects_cmd = GitCommand(
+                project,
+                [
+                    "rev-list",
+                    "--objects",
+                    "--all",
+                    "--reflog",
+                    "--indexed-objects",
+                    "--not",
+                    f"--remotes={project.remote.name}",
+                    "--tags",
+                ],
+                capture_stdout=True,
+                verify_command=True,
+            )
+
+            remote_objects_cmd.Wait()
+
+            pm.update(msg=f"{project.name} | remote repack", inc=0)
+            GitCommand(
+                project,
+                ["pack-objects", os.path.join(pack_dir, "pack")],
+                input=remote_objects_cmd.stdout,
+                capture_stderr=True,
+                capture_stdout=True,
+                verify_command=True,
+            ).Wait()
+
+            # create promisor file for each pack file
+            self._generate_promisor_files(pack_dir)
+
+            local_head_objects_cmd.Wait()
+            local_objects_cmd.Wait()
+
+            pm.update(msg=f"{project.name} | local repack", inc=0)
+            GitCommand(
+                project,
+                ["pack-objects", os.path.join(pack_dir, "pack")],
+                input=local_head_objects_cmd.stdout + local_objects_cmd.stdout,
+                capture_stderr=True,
+                capture_stdout=True,
+                verify_command=True,
+            ).Wait()
+
+            # Swap the old pack directory with the new one.
+            platform_utils.rename(
+                os.path.join(project.objdir, "objects", "pack"),
+                os.path.join(project.objdir, "objects", "pack_old"),
+            )
+            platform_utils.rename(
+                pack_dir,
+                os.path.join(project.objdir, "objects", "pack"),
+            )
+            platform_utils.rmtree(
+                os.path.join(project.objdir, "objects", "pack_old")
+            )
+
+        pm.end()
+        return 0
+
+    def Execute(self, opt, args):
+        projects: List[Project] = self.GetProjects(
+            args, all_manifests=not opt.this_manifest_only
+        )
+
+        ret = self.delete_unused_projects(projects, opt)
+        if ret != 0:
+            return ret
+
+        if not opt.repack:
+            return
+
+        return self.repack_projects(projects, opt)

subcmds/sync.py

@@ -1058,6 +1058,8 @@ later is required to fix a server side protocol bug.
                 verbose=verbose,
             )
             success = syncbuf.Finish()
+        except KeyboardInterrupt:
+            logger.error("Keyboard interrupt while processing %s", project.name)
         except GitError as e:
             logger.error(
                 "error.GitError: Cannot checkout %s: %s", project.name, e
@@ -1500,6 +1502,7 @@ later is required to fix a server side protocol bug.
         if manifest_server.startswith("persistent-"):
             manifest_server = manifest_server[len("persistent-") :]
 
+        # Changes in behavior should update docs/smart-sync.md accordingly.
         try:
             server = xmlrpc.client.Server(manifest_server, transport=transport)
             if opt.smart_sync: