Тестовый скрипт:
#!/usr/bin/wish

set _git  {/usr/bin/git}

proc _git_cmd {name} {
        return [list $::_git $name]
}

proc git {args} {
        set opt [list]

        set cmdp [_git_cmd [lindex $args 0]]
        set args [lrange $args 1 end]

        set result [eval exec $opt $cmdp $args]
        puts stderr "< $result"
        return $result
}

git --version

strace:

pid 13416] pipe([6<pipe:[143743268]>, 7<pipe:[143743268]>]) = 0
[pid 13416] fcntl(6<pipe:[143743268]>, F_SETFD, FD_CLOEXEC) = 0
[pid 13416] fcntl(7<pipe:[143743268]>, F_SETFD, FD_CLOEXEC) = 0
[pid 13416] open("/tmp/tcliCOyqF", O_RDWR|O_CREAT|O_EXCL, 0600) = 9</tmp/tcliCOyqF>
[pid 13416] fcntl(9</tmp/tcliCOyqF>, F_SETFD, FD_CLOEXEC) = 0
[pid 13416] unlink("/tmp/tcliCOyqF")    = 0
[pid 13416] pipe([10<pipe:[143743271]>, 11<pipe:[143743271]>]) = 0
[pid 13416] fcntl(10<pipe:[143743271]>, F_SETFD, FD_CLOEXEC) = 0
[pid 13416] fcntl(11<pipe:[143743271]>, F_SETFD, FD_CLOEXEC) = 0
[pid 13416] close(11<pipe:[143743271]>) = 0
[pid 13416] read(10<pipe:[143743271]>, "", 223) = 0
[pid 13416] close(10<pipe:[143743271]>) = 0
[pid 13416] close(7<pipe:[143743268]>)  = 0
[pid 13416] read(6<pipe:[143743268]>, "", 4096) = 0
[pid 13416] close(6<pipe:[143743268]>)  = 0
[pid 13416] ioctl(9< (deleted)/tmp/tcliCOyqF>, TCGETS, 0x7ffe29879b50) = -1 ENOTTY (Inappropriate ioctl for device)
[pid 13416] getsockname(9< (deleted)/tmp/tcliCOyqF>, 0x7ffe29879bf0, 0x7ffe29879bec) = -1 ENOTSOCK (Socket operation on non-socket)
[pid 13416] wait4(1298893056, 0x7ffe29879bd0, 0, NULL) = -1 ECHILD (No child processes)
[pid 13416] lseek(9< (deleted)/tmp/tcliCOyqF>, 0, SEEK_SET) = 0
[pid 13416] read(9< (deleted)/tmp/tcliCOyqF>, "", 4096) = 0
[pid 13416] close(9< (deleted)/tmp/tcliCOyqF>) = 0
[pid 13416] write(2</dev/pts/13>, "Error in startup script", 23Error in startup script) = 23

Судя по скрипту, проблема адресуется к wish из tk.
Проверялось на tk-8.5.9-alt3

Было
# rpm -V tk
S.......   /usr/bin/wish8.5

то есть проблемы с размером файла.

После переустановки пакета tk всё заработало.

Проблему вызывает запуск
# prelink /usr/bin/wish8.5