[BUG] Escape character appears in final value when escaping single quotes in environment file

[aidaneastcott]

Description

The environment file syntax documentation contains the following example:

• Quotes can be escaped with \.
  • VAR='Let\'s go!' -> Let's go!

Source: https://docs.docker.com/compose/environment-variables/env-file/

However, when I attempt this, VAR has a value of Let\'s go!.

Steps To Reproduce

1. Create an environment file as follows:

# test.env
VAR='Let\'s go!'

2. Create a Compose file as follows:

# compose.yaml
services:
  test:
    image: debian
    env_file: test.env
    command: env

3. Run docker compose up

This is the output I get:

scratch-test-1  | PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
scratch-test-1  | HOSTNAME=ef2eaa14b918
scratch-test-1  | VAR=Let\'s go!
scratch-test-1  | HOME=/root
scratch-test-1 exited with code 0

This is the expected output:

scratch-test-1  | PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
scratch-test-1  | HOSTNAME=ef2eaa14b918
scratch-test-1  | VAR=Let's go!
scratch-test-1  | HOME=/root
scratch-test-1 exited with code 0

Compose Version

Docker Compose version v2.21.0

Docker Environment

Client: Docker Engine - Community
 Version:    24.0.7
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.11.2
    Path:     /usr/libexec/docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  v2.21.0
    Path:     /usr/libexec/docker/cli-plugins/docker-compose

Server:
 Containers: 2
  Running: 0
  Paused: 0
  Stopped: 2
 Images: 3
 Server Version: 24.0.7
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Cgroup Version: 1
 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: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 3dd1e886e55dd695541fdcd67420c2888645a495
 runc version: v1.1.10-0-g18a0cb0
 init version: de40ad0
 Security Options:
  seccomp
   Profile: builtin
 Kernel Version: 5.15.133.1-microsoft-standard-WSL2
 Operating System: Debian GNU/Linux 11 (bullseye)
 OSType: linux
 Architecture: x86_64
 CPUs: 4
 Total Memory: 7.731GiB
 Name: [REDACTED]
 ID: 8020fa55-64b4-46e1-8b70-947218f6c476
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

WARNING: No blkio throttle.read_bps_device support
WARNING: No blkio throttle.write_bps_device support
WARNING: No blkio throttle.read_iops_device support
WARNING: No blkio throttle.write_iops_device support

Anything else?

No response