devcontainer exec does not always propagate SIGTERM to docker exec

[akosyakov]

Steps to reproduce:

• Run devcontainer exec without pty, for instance:

devcontainer exec --container-id 1234abcdefgh -- sleep infinity > /dev/null 2>&1

• Check that on the host machine and inside the container you have infinity sleep process: ps -auxf |grep "infinity"
• Interrupt devcontainer exec with SIGTERM, i.e. kill the process or just interrupt the terminal.
• Check on the host machine the docker process is gone, but inside the container infinity sleep is dangling.

It seems docker exec is terminated without SIGTERM, leading to ungraceful termination.

[chrmarti]

This seems to be moby/moby#9098.