screen: Introduce Xx string escape showing the executed command of a window

either only the executed command ('X') or the whole command line ('x') of
each window is shown.

Signed-off-by: Thomas Renninger <trenn@suse.de>

diff --git a/doc/screen.1 b/doc/screen.1
index 7a0c1de..57352f1 100644
--- a/doc/screen.1
+++ b/doc/screen.1
@@ -3750,6 +3750,10 @@ window; with '+' qualifier: starting with the window after the current
 one.
 .IP W
 all window numbers and names except the current one
+.IP x
+the executed command including arguments running in this windows
+.IP X
+the executed command without arguments running in this windows
 .IP y
 last two digits of the year number
 .IP Y
diff --git a/screen.c b/screen.c
index efb73d3..e8a553c 100644
--- a/screen.c
+++ b/screen.c
@@ -2681,6 +2681,23 @@ int rec;
 	    }
 	  p += strlen(p) - 1;
 	  break;
+	case 'X': case 'x':
+	  if (!win)
+	    break;
+	  if (win->w_cmdargs[0]) {
+	    sprintf(p, "%s", win->w_cmdargs[0]);
+	    p += strlen(p);
+	  }
+	  else
+	    break;
+	  if (*s == 'x') {
+	    for (i = 1; win->w_cmdargs[i]; i++) {
+	      sprintf(p, " %s", win->w_cmdargs[i]);
+	      p += strlen(p);
+	    }
+	  }
+	  p--;
+	  break;
 	case 'l':
 #ifdef LOADAV
 	  *p = 0;