Second attempt at fixing msys terminal width.

Lock the max width on msys-based terminals to 60. I tried a lot of different
things, but I was unable to find a way to detect the correct width in mintty.
Unfortunately this means that terminals that work correctly like ConEmu will
also be capped at 60. C'est la vie.

Of course this does not affect cmd, powershell, etc.

src/cargo/core/shell.rs

@@ -358,8 +358,7 @@ mod imp {
 mod imp {
     extern crate winapi;
 
-    use std::mem;
-    use std::ptr;
+    use std::{cmp, mem, ptr};
     use self::winapi::um::fileapi::*;
     use self::winapi::um::handleapi::*;
     use self::winapi::um::processenv::*;
@@ -395,13 +394,15 @@ mod imp {
             CloseHandle(h);
             if rc != 0 {
                 let width = (csbi.srWindow.Right - csbi.srWindow.Left) as usize;
-                // Some terminals, such as mintty, always return 79 instead of
-                // the actual width. In that case, use a conservative value.
-                if width == 79 {
-                    return Some(60);
-                } else {
-                    return Some(width);
-                }
+                // Unfortunately cygwin/mintty does not set the size of the
+                // backing console to match the actual window size. This
+                // always reports a size of 80 or 120 (not sure what
+                // determines that). Use a conservative max of 60 which should
+                // work in most circumstances. ConEmu does some magic to
+                // resize the console correctly, but there's no reasonable way
+                // to detect which kind of terminal we are running in, or if
+                // GetConsoleScreenBufferInfo returns accurate information.
+                return Some(cmp::min(60, width));
             }
             return None;
         }