How to build and debug git-gui?

[ToBoMi]

• I was not able to find an open or closed issue matching what I'm seeing

Setup

• Which version of Git for Windows are you using? Is it 32-bit or 64-bit? 64bit

$ git --version --build-options

git version 2.45.2.GIT
cpu: AMD64
no commit associated with this build
sizeof-long: 4
sizeof-size_t: 8
shell-path: /bin/sh
feature: fsmonitor--daemon

• Which version of Windows are you running? Vista, 7, 8, 10? Is it 32-bit or 64-bit?

$ cmd.exe /c ver

Microsoft Windows [Version 10.0.19045.4529]

• What options did you set as part of the installation? Or did you choose the
  defaults?

# One of the following:
> type "C:\Program Files\Git\etc\install-options.txt"
> type "C:\Program Files (x86)\Git\etc\install-options.txt"
> type "%USERPROFILE%\AppData\Local\Programs\Git\etc\install-options.txt"
> type "$env:USERPROFILE\AppData\Local\Programs\Git\etc\install-options.txt"
$ cat /etc/install-options.txt

• Any other interesting things about your environment that might be related
  to the issue you're seeing?

I build using Visual Studio and git-for-windows opened as a folder (As mentioned in the Readme).
Confugration and Build succeeds - git.exe starts.

Details

• Which terminal/shell are you running Git from? e.g Bash/CMD/PowerShell/other

I don't really know. I use the Visual Studio Debugger/Launcher - maybe it is just cmd.

• What commands did you run to trigger this issue? If you can provide a
  Minimal, Complete, and Verifiable example
  this will help us understand the issue.

• What did you expect to occur after running these commands?

Not applicable - I have a question about building.

• What actually happened instead?

• If the problem was occurring with a specific repository, can you provide the
  URL to that repository to help us with testing?

My question

I would like to contribute to git-gui and therefore want to build it. It doesn't necessarily needs to be build since it is tcl script based, but I cannot find a tcl script for git gui - like for gitk.
I also saw that the git installation insalled by using the installer of git-for-windows comes with a git-gui.exe (not tcl-only) and the readme in the git-gui folder mentions a "build" using make. This seems to be not really needed, but can be done.
Since gitk works without build (tcl) I wonder how git-gui is build here. I found no specific instructions for git-gui and I don't really know how to use make for git-for-windows.
I can build git (git.exe) and run gitk (tclsh.exe .\\gitk-git\\gitk)

Can someone help me start debugging of git-gui?

[dscho]

It doesn't necessarily needs to be build since it is tcl script based, but I cannot find a tcl script for git gui - like for gitk.

It is here: https://github.com/git-for-windows/git/blob/HEAD/git-gui/git-gui.sh

But that is not all there is to it, it comes with a library of Tcl files at https://github.com/git-for-windows/git/tree/HEAD/git-gui/lib and with a Windows-specific wrapper: https://github.com/git-for-windows/git/blob/HEAD/git-gui/windows/git-gui.sh

the installer of git-for-windows comes with a git-gui.exe (not tcl-only)

Indeed, this is another wrapper that is copied to /cmd/git-gui.exe.

the readme in the git-gui folder mentions a "build" using make.

Right, and the idea was to replicate the same functionality in the CMake configuration, but that has not happened yet:

git/contrib/buildsystems/CMakeLists.txt

Line 127 in f46b4dc

#TODO gitk git-gui gitweb

Can someone help me start debugging of git-gui?

The easiest way is to use a PortableGit and edit mingw64/libexec/git-core/git-gui.tcl (which is a copy of git-gui/git-gui.sh) and the files in mingw64/share/git-gui/lib/ (which are copies of the git-gui/lib/ files) and maybe even the small wrapper in mingw64/libexec/git-core/git-gui.tcl (which is a copy of git-gui/windows/git-gui.sh).

Once you implemented a new feature or a bug fix that way, copy the edited files over the source files and commit. (You may want to stage in a more fine-grained manner, e.g. using Git GUI itself, seeing as there are some placeholders that are interpolated during a make run.)

[ToBoMi]

Thanks for your detailed response.
I was able to start developing in a copy of my existing git installation.

It is a bit strange to use an installation and not the source code, but since there is no other way I guess I have to live with it.