I’m still making best guesses here and I don’t know why this is happening for your system. One thing that sticks out is the Git version: Git-128) (with a closing parenthesis).
This is what I get locally:
$ netlify lm:info
✔ Checking Git version [2.26.2]
✔ Checking Git LFS version [2.10.0]
✔ Checking Git LFS filters
✔ Checking Netlify's Git Credentials version [0.1.9]
I believe version “Git-128” is the stock Git client installed with MacOS (or maybe with Xcode). This might not be the same Git that the git credential helper is designed for and I don’t know if that version is supported or not. (I’m having trouble getting more information about what git version that actually is as it doesn’t match the versioning system for Git):
So this might just come down to an unsupported Git client version. You can see the path to git with which and then check that version directly with the fully-qualified path name (FQPN):
$ which git
/usr/local/bin/git
$ /usr/local/bin/git version
git version 2.26.2
You can also look around for other versions of git installed:
$ find / -type f -iname "git" 2>/dev/null
/usr/bin/git
/usr/local/Homebrew/Library/Homebrew/shims/scm/git
/usr/local/Cellar/git/2.26.2/bin/git
/usr/local/Cellar/git/2.26.2/share/git-core/contrib/mw-to-git/bin-wrapper/git
/Library/Developer/CommandLineTools/usr/bin/git
/System/Volumes/Data/usr/local/Homebrew/Library/Homebrew/shims/scm/git
/System/Volumes/Data/usr/local/Cellar/git/2.26.2/bin/git
/System/Volumes/Data/usr/local/Cellar/git/2.26.2/share/git-core/contrib/mw-to-git/bin-wrapper/git
/System/Volumes/Data/Library/Developer/CommandLineTools/usr/bin/git
I think I proved the Apple version hypothesis:
$ /usr/bin/git version
git version 2.24.1 (Apple Git-126)
Above is Git-126) (closing parenthesis and all) similar to the Git-128) on your system.
So, just changing the PATH environment variable to use the Homebrew version of git might resolve this:
If that doesn’t work, please let us know.