Add -u git to docs when using docker exec with root installation

[scribblemaniac]

This fixes a minor issue in the documentation for SSH Container Passthrough for non-rootless installs. The non-rootless Dockerfile and docker-compose do not set USER/user instructions so docker exec will run as root by default. While running as root, gitea commands will refuse to execute, breaking these approaches. For containers built with the rootless instructions, docker exec will run as git by default so this is not necessary in that case.

This issue was already discussed in #19065, but it does not appear this part of the issue was ever added to the documentation.

[6543]

isn't that only valid for the rootles containers?

[scribblemaniac]

No. The docker exec command is run in the container as the same user that the build the container if no -u argument is provided. The rootless containers are built as git (not root) so they don't default to root, so they don't need this. The root containers are built as root (not git), so it docker exec defaults to root, so they need this.

With root image:

# id command output when starting the container
$ docker run --entrypoint id gitea/gitea:1.21.5
uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),11(floppy),20(dialout),26(tape),27(video)
# id command output when execing into an existing container
$ docker exec gitea id
uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),11(floppy),20(dialout),26(tape),27(video)

With rootless image:

# id command output when starting the container
$ docker run --entrypoint id gitea/gitea:1.21.5-rootless
uid=1000(git) gid=1000(git) groups=1000(git)
# id command output when execing into an existing container
$ docker exec gitea_rootless id
uid=1000(git) gid=1000(git) groups=1000(git)

The only reason the gitea server even starts with the root configuration is because it is run with su-exec git here. But docker exec does not use the entrypoint script, so it won't do that automatically like it does for docker run.

[GiteaBot]

I was unable to create a backport for 1.22. @scribblemaniac, please send one manually. 🍵

go run ./contrib/backport 29314
...  // fix git conflicts if any
go run ./contrib/backport --continue

[scribblemaniac]

I was unable to create a backport for 1.22. @scribblemaniac, please send one manually. 🍵

I'm assuming this is a bug with the bot. It appears to have been backported to 1.22 just fine in #30259.

[techknowlogick]

@scribblemaniac yup, all is well, nothing more needed for you to do. Thanks for the PR :)