fix dockerfile local dir

[junnplus]

Signed-off-by: Ye Sijun junnplus@gmail.com

Fixes: #1191

In addition, check in advance whether the dockerfile file exists.

before:

[N] ❯ sudo nerdctl build -t backstage:dev ..
[+] Building 0.0s (2/2) FINISHED
 => [internal] load .dockerignore                                                                                                                                                                                           0.0s
 => => transferring context: 2B                                                                                                                                                                                             0.0s
 => [internal] load build definition from Dockerfile                                                                                                                                                                        0.0s
 => => transferring dockerfile: 2B                                                                                                                                                                                          0.0s
error: failed to solve: failed to read dockerfile: open /tmp/buildkit-mount1687483572/Dockerfile: no such file or directory
FATA[0000] unrecognized image format

after:

[N] ❯ sudo nerdctl build -t backstage:dev ..
FATA[0000] lstat /home/jun/Documents/workspace/my-backstage/packages/Dockerfile: no such file or directory

[manugupt1]

Q: Why do we need builder prune? Won't these slow our tests?

[junnplus]

cc @ktock

[ktock]

@manugupt1 @junnplus This was to ensure all content (possibly leased by BuildKit) in the content store gets pruned after each test. Tests may check the behaviour of pulling blobs and contents remaining in the content store unexpectedly skip these operations.But yes, we may improve this by removing defer base.Cmd("builder", "prune").Run() and instead adding rmiAll() (defined in image_encrypt_linux_test.go) to tests (if exist) requiring clean content store. Thanks for pointing this out :)

[manugupt1]

thanks for the changes!

[Zheaoli]

LGTM

[AkihiroSuda]

How does this happen?

Can't find "unreachable" error in the code
https://cs.opensource.google/go/go/+/refs/tags/go1.18.3:src/os/getwd.go;l=22

[junnplus]

I actually don't know what happened, Getwd returns a strange path during rootless testing.
(unreachable)/tmp/TestBuildWithDockerfile2096791215/001/text/Dockerfile

https://github.com/containerd/nerdctl/runs/7196804919?check_suite_focus=true#step:5:1004

[AkihiroSuda]

Thanks