Custom commands fail to run git alias "start" commands 90% of the time

[howeaj]

Version info

• OS: Windows 10
• Build: 3211
• Browser: Google Chrome Version 89.0.4389.90 (Official Build) (64-bit)
• git: version 2.31.0.windows.1

Description

When SublimeMerge runs a custom command, which runs a git alias, which tries to use "start" to open some URL in the default browser, it fails to open anything 90% of the time. (but occasionally does successfully open it)

I've been unable to figure out any particular condition that causes it to work or not. Generally clicking around in the browser, opening new tabs etc before running the command in SublimeMerge seems to help it work.

The alias works perfectly running git from the command line. (and I have configured SublimeMerge to use the same git binary as the commandline)

I'd imagine custom commands which open an URL (to a pull request, to an issue tracker, etc) to be quite a common need, e.g. https://forum.sublimetext.com/t/github-gitlab-bitbucket-integration-commands-menu-items/53893

Steps to reproduce

git config alias.test "!start http://google.com" add to Default.sublime-commands in %APP_DATA%\Sublime Merge\Packages\User:

[
    {
        "caption": "Open google.com",
        "command": "git",
        "args": {"argv": ["test"]}
    }
]

Expected behavior

The URL opens in the default browser, as it does when running the alias from the commandline.