Just checked gitk, it seems to work fine including children windows.
This problem seems to affect git-gui only.
On Thu, Nov 29, 2018 at 5:16 AM Eric Sunshine [off-list ref] wrote:

On Wed, Nov 28, 2018 at 2:29 PM Stefan Beller [off-list ref] wrote:

quoted

On Wed, Nov 28, 2018 at 6:13 AM Kenn Sebesta [off-list ref] wrote:

quoted

v2.19.2, installed from brew on macOS Mojave 14.2.1.

`git-gui` is my much beloved go-to tool for everything git.
Unfortunately, on my new Macbook Air it seems to have a bug. When I
first load the program, the parent window populates normally with the
stage/unstaged and diff panes. However, when I click Push, the child
window is completely blank. The frame is there, but there is no
content.

Looking through the mailing list archive, this
seemed to be one of the last relevant messges
https://public-inbox.org/git/20180724065120.7664-1-sunshine@sunshineco.com/

I was hoping that Junio would patch-monkey that one since that
crash-at-launch makes gitk unusable for Mojave users, but apparently
it never got picked up.

Anyhow, the issue fixed by that patch has to do with 'osascript' on
Apple, and it's the only such invocation in the source code of
gitk/git-gui. The 'osascript' invocation merely attempts to foreground
the application at launch, so is almost certainly unrelated to the
above reported behavior. Somebody running Mojave will likely need to
spend some time debugging it. (Unfortunately, I'm a couple major
releases behind and don't plan on upgrading.)