Supporting Alpine Linux

[arschles]

I tried to build mc for Alpine Linux (inside an alpine:3.1 docker container). As these instructions say, musl doesn't support the os/user package yet. As this program uses os/user to get the home directory (to get the config file), Alpine builds fail at runtime, even when -C is passed via the CLI.

Right now, this PR removes the entire dependency on os/user, but the final version could use build constraints to toggle usage of os/user. Or perhaps there's an easier way to get this working that I haven't thought of. Thoughts?

[harshavardhana]

Thanks for trying out 'mc' in docker.

The right fix is to use - https://github.com/minio/minio/blob/8046b24b975a26d659bda12797a30631bb427e8f/utils.go#L63 - which we did with our minio server.

Can you bring this change in this patch?

[harshavardhana]

Following change needs to be incorporated into your diff. @arschles -

This way it will work in a portable way.

-// user.Current is not implemented on 32bit, falling back and using a workaround instead.
+// user.Current is not implemented on 32bit and statically compiled binaries.
+// Following code provides valid workaround for each of these situations.
 func userCurrent() (*user.User, *probe.Error) {
+       // Set env variable to indicate 'mc' is being run inside DOCKERIMAGE.
+       if os.Getenv("DOCKERIMAGE") == "1" {
+               wd, err := os.Getwd()
+               if err != nil {
+                       return nil, probe.NewError(err)
+               }
+               return &user.User{Uid: "0", Gid: "0", Username: "root", Name: "root", HomeDir: wd}, nil
+       }
        // Remove this check if golang fixes their code to support 32bit properly for user.Current.
        if runtime.GOARCH == "386" && runtime.GOOS == "linux" {
                return &user.User{

[arschles]

@harshavardhana thanks for the direction.

I ported the code that you suggested and it looks like the code already has the pertinent changes in the diff you pasted.

I've also merged from master. Can you please let me know if you prefer I rebase?

[harshavardhana]

@arschles - can you squash these commits into single change?

[harshavardhana]

Thanks for your work.

[arschles]

@harshavardhana I wasn't paying attention to what I was doing and messed up the squash. I'll open a new PR for this change