Git 2.29.2 difftool no longer working

[bit-bash]

• [X ] 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?

$ git --version --build-options

git version 2.29.2.windows.2
cpu: x86_64
built from commit: 3464b98ce6803c98bf8fb34390cd150d66e4a0d3
sizeof-long: 4
sizeof-size_t: 8
shell-path: /bin/sh

• 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 10.0.18363.657]

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

# One of the following:
$ cat /etc/install-options.txt

Editor Option: Nano
Custom Editor Path:
Default Branch Option:
Path Option: Cmd
SSH Option: OpenSSH
Tortoise Option: false
CURL Option: OpenSSL
CRLF Option: CRLFAlways
Bash Terminal Option: MinTTY
Git Pull Behavior Option: Merge
Use Credential Manager: Disabled
Performance Tweaks FSCache: Enabled
Enable Symlinks: Disabled
Enable Pseudo Console Support: Disabled

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

I am trying to invoke BeyondCompare with git difftool -d HEAD~1
Section in ~/.gitconfig is:

[diff]
        tool = bc4
[difftool "bc4"]
        cmd = \"c:/program files/beyond compare 4/bcompare.exe\" \"$LOCAL\" \"$REMOTE\"

Note, this WORKS when I downgrade to git 2.28.0, and there are no other changes.

Details

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

Bash

• 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.

git difftool -d HEAD~1

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

I expected BeyondCompare to launch, showing the differences between working dir and previous commit.

• What actually happened instead?

There is a slight delay, then nothing happens and I'm back to the shell prompt.

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

Tried many different repo, I can reproduce on any of them.

I have reproduced this issue on two different Windows 10 systems.
Current workaround is to use git 2.28.0.

[dscho]

Have you looked whether the log produced with GIT_TRACE contains anything interesting?

[bit-bash]

Have you looked whether the log produced with GIT_TRACE contains anything interesting?

I've installed 2.28.0, but when I get a chance, I'll re-install 2.29.2 and run again with GIT_TRACE.

[dscho]

I've installed 2.28.0, but when I get a chance, I'll re-install 2.29.2

FWIW if you want to keep your v2.28.0 but just want to run the test I asked for with v2.29.2, you can install a Portable Git (which will not overwrite your existing installation).

[bit-bash]

Good suggestion! Results are inconclusive - I can't see any smoking gun in the trace logs.

Installed 2.28.0 works with: git difftool -d HEAD~1
Portable (or previously installed 2.29.2) does not work with: git difftool -d HEAD~1

trace2.28.0.txt
trace2.29.2.txt

[dscho]

Okay, I think I know what is going on: 83bbf9b, contributes via https://lore.kernel.org/git/[email protected]/, broke it. Basically, it overrides the user setup because bc4 and bc sound so similar. My current working hypothesis is that this fixes it:

diff --git a/git-mergetool--lib.sh b/git-mergetool--lib.sh
index 2defef28cd93..7225abd81122 100644
--- a/git-mergetool--lib.sh
+++ b/git-mergetool--lib.sh
@@ -138,6 +138,10 @@ setup_user_tool () {
 	merge_cmd () {
 		( eval $merge_tool_cmd )
 	}
+
+	list_tool_variants () {
+		echo "$tool"
+	}
 }
 
 setup_tool () {

If you get a chance, would you mind making that change manually (by editing /mingw64/libexec/git-core/git-mergetool--lib, you might need administrator privileges, adding the list_tool_variants () definition at the end of the setup_user_tool () function)?

I will try to get this patch into a mergeable and submittable form in the meantime.

[bit-bash]

If you get a chance, would you mind making that change manually (by editing /mingw64/libexec/git-core/git-mergetool--lib, you might need administrator privileges, adding the list_tool_variants () definition at the end of the setup_user_tool () function)?

I made the edit (using portable git) and I can confirm this fixes the issue! Yay!

[dscho]

Good, thanks for testing!

[dscho]

@bit-bash if you want to run a fixed version, please install the latest snapshot.