Support native cmd for ssh/scp

[vagetablechicken]

Feature Request

Is your feature request related to a problem? Please describe:

Nope.
Describe the feature you'd like:

tiup cluster executor can use native ssh. That's nice. But it can only use "ssh"(in PATH). We can't define the command we want to use.

tiup/pkg/cluster/executor/ssh.go

Line 304 in 91c5f94

args := []string{"ssh", "-o", "StrictHostKeyChecking=no"}

Describe alternatives you've considered:
What if we use other ssh tools to connect the hosts? e.g. some ssh tools which contain security permissions.

Use alias could solve it. But it's not a good method.

I think supporting native cmd is a good way.
Teachability, Documentation, Adoption, Migration Strategy:

[AstroProfundis]

I think we could support that by adding a new argument to specify the path of an alternative SSH executable binary, something like --ssh-path or so.

[vagetablechicken]

I think we could support that by adding a new argument to specify the path of an alternative SSH executable binary, something like --ssh-path or so.

Agree entirely. I'd want --scp-path too. If --ssh-path/--scp-path is not specified, it will use "ssh"/"scp".

[9547]

if --ssh-path or --scp-path is specified, seem too much code has to refactor! Or should we set two global envars, such as TIUP_NATIVE_SSH_PATH to specify the alternative ssh executable binary, and fetch it before

tiup/pkg/cluster/executor/ssh.go

Line 304 in 91c5f94

args := []string{"ssh", "-o", "StrictHostKeyChecking=no"}

ssh := "ssh"

isExec := func(mode os.FileMode) bool { return mode&0111 == 0111 }
if env := os.Getenv(localdata.EnvNameNativeSSHPath); env != "" {
    if info, err := os.Stat(env); err == nil && !info.IsDir() && isExec(info.Mode()) {
        ssh = env
    }
}

args := []string{ssh, "-o", "StrictHostKeyChecking"}

[vagetablechicken]

@9547 Good advice. It's not a universal need, so ENV is OK.

[lucklove]

@9547 Do you have any interest on this? If so, you'd better do it after #699 been merged (in case of conflicts). Otherwise I will do it in #699

[9547]

@9547 Do you have any interest on this? If so, you'd better do it after #699 been merged (in case of conflicts). Otherwise I will do it in #699

I will send an PR tonight

[lucklove]

@9547 Do you have any interest on this? If so, you'd better do it after #699 been merged (in case of conflicts). Otherwise I will do it in #699

I will send an PR tonight

Ok, then I'll not merge #699 util your PR is merged