After cygwin upgrade, Emacs shell buffers with colors are corrupted

[David Karr]

Yesterday I upgraded Cygwin, which I hadn't done in a while. I had recently
upgraded my Windows 10 OS from build 1709 to 1809 (yes, those are correct).

My current Emacs version is 26.3, but I don't know what it was before the
upgrade.

If I create a shell buffer and execute a command that produces plain,
uncolored output, it appears to work fine.  However, output from "Maven"
has always been colorized for me, and it's always worked fine.  Today, I'm
seeing that the output is severely corrupted.  If I pipe the output into a
file and view that, which doesn't have colors, the contents are fine. I
also ran the same process in a mintty window, which is colorized in the
same way, and that is also working fine.

For instance, if this is what I see in a mintty buffer:
-----------------------
[WACDTL03DK068X:~/git/cartms] mvn package
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option
MaxPermSize=128m; sup
port was removed in 8.0
[INFO] Scanning for projects...
[WARNING]
...
-------------------------

What I see in the Emacs shell buffer is something like this:
-------------------------
[WACDTL03DK068X:~/git/cartms] mvn package
[WACDTL03DK068X:~/git/cartms] [WACDTL03DK068X:~/git/cartms] Java
HotSpot(TM) 64-
Bit Server VM warning:ignoring option MaxPermSize=128m; support was removed
in
8.0
[INFO] Scanning for projects...[
[WARNING] l





....
---------------------------

The first thing I see is that it prints the shell prompt twice AFTER
pressing enter on the command line to run. That might possibly be an issue
with my Bash dot files, but this didn't happen before the Cygwin upgrade,
and it doesn't happen in the mintty window.

After that, it gets even worse.  The "Java HotSpot ..." line prints in
three lines, instead of a single line.  Then, the first "WARNING" line has
the "l" at the end of the line, and then numerous blank lines.  The rest of
the output is mangled in other ways.

Any ideas what might be wrong here?