"gitk &" closes parent bash upon exit

[Illia Bobyr]

  Configuration Information:
Machine: i686
OS: cygwin
Compiler: gcc-4
Compilation CFLAGS:  -DPROGRAM='bash.exe' -DCONF_HOSTTYPE='i686' 
-DCONF_OSTYPE='cygwin' -DCONF_MACHTYPE='i686-pc-cygwin' 
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' 
-DSHELL -DHAVE_CONFIG_H -DRECYCLES_PIDS   -I.  
-I/usr/src/bash-3.2.51-24/src/bash-3.2 
-I/usr/src/bash-3.2.51-24/src/bash-3.2/include 
-I/usr/src/bash-3.2.51-24/src/bash-3.2/lib   -O2 -pipe
uname output: CYGWIN_NT-5.1 wron-ibobyr 1.7.7(0.230/5/3) 2010-08-31 
09:58 i686 Cygwin
Machine Type: i686-pc-cygwin

Bash Version: 3.2
Patch Level: 51
Release Status: release

Description:
     I see this problem only with gitk (that is a TCL script).  It 
appeared about a couple of month ago.  I update all the packages in my 
Cygwin installation almost weekly.  It is probably possible to figure 
out which bash and/or gitk update was the one that introduced the 
problem but I did not do it yet.
     When I do "gitk &" upon gitk exit the parent bash process 
terminates as well.
     When I do "(gitk &)" it works fine.  There does not seem to be any 
crash dumps.  But sometimes bash outputs "Logout" before it exits just 
as if I would press ^D on prompt.  I have tried putting "gitk &" call 
into a script and adding traps for all possible signals but none seemed 
to be fired.
     You do not have to be in a directory that is a Git repository.

     It may be a Cygwin specific problem.  Approximately at the time the
problem appeared cygwin.dll was also updated.

     I hope that maybe someone with more knowledge in the relevant areas
may suggest a simpler test case and/or a direction to search for a 
simpler test case as using whole gitk that is a big TCL script.  By the 
way "info patchlevel" on my Cygwin TCL says "8.4.1"

Repeat-By:
     1. gitk &
     2. If you are not in a Git repository just close the dialog by 
selecting "OK" otherwise close the gitk window.
     3. The parent bash exits.

Fix:
     Running gitk in a subshell works fine.