Allow specifying executable in artifact section and skip bash from WSL (#1169)

## Changes
Allow specifying executable in artifact section

```
artifacts:
  test:
    type: whl
    executable: bash
    ...
```

We also skip bash found on Windows if it's from WSL because it won't be
correctly executed, see the issue above

Fixes #1159

bundle/config/artifact.go

@@ -42,6 +42,8 @@ type Artifact struct {
 	Files        []ArtifactFile `json:"files,omitempty"`
 	BuildCommand string         `json:"build,omitempty"`
 
+	Executable exec.ExecutableType `json:"executable,omitempty"`
+
 	paths.Paths
 }
 
@@ -50,7 +52,14 @@ func (a *Artifact) Build(ctx context.Context) ([]byte, error) {
 		return nil, fmt.Errorf("no build property defined")
 	}
 
-	e, err := exec.NewCommandExecutor(a.Path)
+	var e *exec.Executor
+	var err error
+	if a.Executable != "" {
+		e, err = exec.NewCommandExecutorWithExecutable(a.Path, a.Executable)
+	} else {
+		e, err = exec.NewCommandExecutor(a.Path)
+		a.Executable = e.ShellType()
+	}
 	if err != nil {
 		return nil, err
 	}

libs/exec/exec.go

@@ -2,11 +2,24 @@ package exec
 
 import (
 	"context"
+	"fmt"
 	"io"
 	"os"
 	osexec "os/exec"
 )
 
+type ExecutableType string
+
+const BashExecutable ExecutableType = `bash`
+const ShExecutable ExecutableType = `sh`
+const CmdExecutable ExecutableType = `cmd`
+
+var finders map[ExecutableType](func() (shell, error)) = map[ExecutableType](func() (shell, error)){
+	BashExecutable: newBashShell,
+	ShExecutable:   newShShell,
+	CmdExecutable:  newCmdShell,
+}
+
 type Command interface {
 	// Wait for command to terminate. It must have been previously started.
 	Wait() error
@@ -61,6 +74,22 @@ func NewCommandExecutor(dir string) (*Executor, error) {
 	}, nil
 }
 
+func NewCommandExecutorWithExecutable(dir string, execType ExecutableType) (*Executor, error) {
+	f, ok := finders[execType]
+	if !ok {
+		return nil, fmt.Errorf("%s is not supported as an artifact executable, options are: %s, %s or %s", execType, BashExecutable, ShExecutable, CmdExecutable)
+	}
+	shell, err := f()
+	if err != nil {
+		return nil, err
+	}
+
+	return &Executor{
+		shell: shell,
+		dir:   dir,
+	}, nil
+}
+
 func (e *Executor) StartCommand(ctx context.Context, command string) (Command, error) {
 	ec, err := e.shell.prepare(command)
 	if err != nil {
@@ -99,3 +128,7 @@ func (e *Executor) Exec(ctx context.Context, command string) ([]byte, error) {
 
 	return res, cmd.Wait()
 }
+
+func (e *Executor) ShellType() ExecutableType {
+	return e.shell.getType()
+}

libs/exec/shell.go

@@ -8,6 +8,7 @@ import (
 
 type shell interface {
 	prepare(string) (*execContext, error)
+	getType() ExecutableType
 }
 
 type execContext struct {

libs/exec/shell_bash.go

@@ -3,6 +3,7 @@ package exec
 import (
 	"errors"
 	osexec "os/exec"
+	"strings"
 )
 
 type bashShell struct {
@@ -33,5 +34,14 @@ func newBashShell() (shell, error) {
 		return nil, nil
 	}
 
+	// Skipping WSL bash if found one
+	if strings.Contains(out, `\Windows\System32\bash.exe`) || strings.Contains(out, `\Microsoft\WindowsApps\bash.exe`) {
+		return nil, nil
+	}
+
 	return &bashShell{executable: out}, nil
 }
+
+func (s bashShell) getType() ExecutableType {
+	return BashExecutable
+}

libs/exec/shell_cmd.go

@@ -36,3 +36,7 @@ func newCmdShell() (shell, error) {
 
 	return &cmdShell{executable: out}, nil
 }
+
+func (s cmdShell) getType() ExecutableType {
+	return CmdExecutable
+}

libs/exec/shell_sh.go

@@ -35,3 +35,7 @@ func newShShell() (shell, error) {
 
 	return &shShell{executable: out}, nil
 }
+
+func (s shShell) getType() ExecutableType {
+	return ShExecutable
+}