cmd/run: Don't allocate pseudo-TTY if not connected to terminal

Passing '--tty' to 'podman exec' unconditionally causes Podman to
allocate a pseudo-TTY for the command execution. This causes problems
with piping (values not being piped in and values being piped out with
carriage return at the end of a line). The solution is to track the
presence of a terminal on stdin/stdout and based on its presence use the
'--tty' flag.

Original behaviour:
; echo foo | toolbox run less

; toolbox echo foo | od -c
0000000   f   o   o  \r  \n
0000005

New behaviour:
; echo foo | toolbox run less
foo

; toolbox echo foo | od -c
0000000   f   o   o  \n
0000004

As seen in the 'Piping in' example, the value gets only printed into
stdout. Not ideal from the point of view of using 'less' (or similar
tools) but still a move forward.

Based on a discussion in Podman's bugtracker[0].

Fixes https://github.com/containers/toolbox/issues/157
Fixes https://github.com/containers/toolbox/issues/848

[0] https://github.com/containers/podman/issues/9718

https://github.com/containers/toolbox/pull/1013

src/cmd/run.go

@@ -26,6 +26,7 @@ import (
 	"github.com/containers/toolbox/pkg/podman"
 	"github.com/containers/toolbox/pkg/shell"
 	"github.com/containers/toolbox/pkg/utils"
+	"github.com/mattn/go-isatty"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 )
@@ -453,9 +454,12 @@ func constructExecArgs(container string,
 
 	execArgs = append(execArgs, detachKeys...)
 
+	if isatty.IsTerminal(os.Stdin.Fd()) && isatty.IsTerminal(os.Stdout.Fd()) {
+		execArgs = append(execArgs, "--tty")
+	}
+
 	execArgs = append(execArgs, []string{
 		"--interactive",
-		"--tty",
 		"--user", currentUser.Username,
 		"--workdir", workDir,
 	}...)