helper = "/path/to/my/helper --with-arguments"
# or you can specify your own shell snippet
-[credential]
- helper = "!f() { echo \"password=$(cat $HOME/.secret)\"; }; f"
+[credential "https://example.com"]
+ username = your_user
+ helper = "!f() { test \"$1\" = get && echo \"password=$(cat $HOME/.secret)\"; }; f"
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Generally speaking, rule (3) above is the simplest for users to specify.