Add envar to replace shallow clones with partial

An investigation go/git-repo-shallow shows a number of problems
when doing a shallow git fetch/clone. This change introduces an
environment variable REPO_ALLOW_SHALLOW. When this environment variable
is set to 1 during a repo init or repo sync all shallow git fetch
commands are replaced with partial fetch commands. Any shallow
repository needing update is unshallowed. This behavior continues until
a subsequent repo sync command is run with REPO_ALLOW_SHALLOW set to 1.

Bug: b/274340522
Change-Id: I1c3188270629359e52449788897d9d4988ebf280
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/374754
Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Tested-by: Jason Chang <jasonnc@google.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/subcmds/init.py b/subcmds/init.py
index 9946466d..6d7fd857 100644
--- a/subcmds/init.py
+++ b/subcmds/init.py
@@ -20,6 +20,8 @@ from command import InteractiveCommand, MirrorSafeCommand
 from git_command import git_require, MIN_GIT_VERSION_SOFT, MIN_GIT_VERSION_HARD
 from wrapper import Wrapper
 
+_REPO_ALLOW_SHALLOW = os.environ.get("REPO_ALLOW_SHALLOW")
+
 
 class Init(InteractiveCommand, MirrorSafeCommand):
     COMMON = True
@@ -125,6 +127,9 @@ to update the working directory files.
         # manifest project is special and is created when instantiating the
         # manifest which happens before we parse options.
         self.manifest.manifestProject.clone_depth = opt.manifest_depth
+        clone_filter_for_depth = (
+            "blob:none" if (_REPO_ALLOW_SHALLOW == "0") else None
+        )
         if not self.manifest.manifestProject.Sync(
             manifest_url=opt.manifest_url,
             manifest_branch=opt.manifest_branch,
@@ -140,6 +145,7 @@ to update the working directory files.
             partial_clone=opt.partial_clone,
             clone_filter=opt.clone_filter,
             partial_clone_exclude=opt.partial_clone_exclude,
+            clone_filter_for_depth=clone_filter_for_depth,
             clone_bundle=opt.clone_bundle,
             git_lfs=opt.git_lfs,
             use_superproject=opt.use_superproject,