Can't build image via git URL when git repo has submodules

[kriddile]

Description

When invoking docker build with a git URL, if the git reference being checked out contains a reference to a submodule that is not at the head of a branch or recent tag in the submodule's repo, the operation fails.

Steps to reproduce the issue:

1. docker build <git URL with a submodule reference not at a branch head or recent tag in the submodule repo>

Describe the results you received:

unable to prepare context: unable to 'git clone' to temporary context directory: error initializing submodules: Submodule 'Foo' (git@github.com:foo/bar.git) registered for path 'Foo'
Cloning into '/private/var/folders/86/ddj24jnj17jf1vjx2s_fmw8w0000gn/T/docker-build-git585701942/Foo'...
error: Server does not allow request for unadvertised object 34ad12fa10bfefc73e027940753d9d70845e4a89
Fetched in submodule path 'Foo', but it did not contain 34ad12fa10bfefc73e027940753d9d70845e4a89. Direct fetching of that commit failed.
: exit status 1

Describe the results you expected:
Successfully built

Additional information you deem important:
I believe this problem is caused by docker build cloning the requested git repository with the --depth=0 flag. The documentation makes no mention of --depth=0 being used.

Output of docker version:

Client: Docker Engine - Community
 Version:           19.03.5
 API version:       1.40
 Go version:        go1.12.12
 Git commit:        633a0ea
 Built:             Wed Nov 13 07:22:34 2019
 OS/Arch:           darwin/amd64
 Experimental:      false

Server: Docker Engine - Community
 Engine:
  Version:          19.03.5
  API version:      1.40 (minimum version 1.12)
  Go version:       go1.12.12
  Git commit:       633a0ea
  Built:            Wed Nov 13 07:29:19 2019
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          v1.2.10
  GitCommit:        b34a5c8af56e510852c35414db4c1f4fa6172339
 runc:
  Version:          1.0.0-rc8+dev
  GitCommit:        3e425f80a8c931f88e6d94a8c831b9d5aa481657
 docker-init:
  Version:          0.18.0
  GitCommit:        fec3683

Output of docker info:

Client:
 Debug Mode: false

Server:
 Containers: 16
  Running: 0
  Paused: 0
  Stopped: 16
 Images: 11
 Server Version: 19.03.5
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Native Overlay Diff: true
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: b34a5c8af56e510852c35414db4c1f4fa6172339
 runc version: 3e425f80a8c931f88e6d94a8c831b9d5aa481657
 init version: fec3683
 Security Options:
  seccomp
   Profile: default
 Kernel Version: 4.19.76-linuxkit
 Operating System: Docker Desktop
 OSType: linux
 Architecture: x86_64
 CPUs: 6
 Total Memory: 1.943GiB
 Name: docker-desktop
 ID: EYRW:KLGG:S7GY:M7YZ:FHTL:KX2P:Z4NJ:MJZG:BFQV:KAWB:FBC4:3O7O
 Docker Root Dir: /var/lib/docker
 Debug Mode: true
  File Descriptors: 36
  Goroutines: 52
  System Time: 2020-03-03T21:14:12.232032346Z
  EventsListeners: 3
 HTTP Proxy: gateway.docker.internal:3128
 HTTPS Proxy: gateway.docker.internal:3129
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false
 Product License: Community Engine