If reauth is required, show the full command-line path of the binary

[rogerhu]

The error message that gets printed out tells me to login again. However, it doesn't show the full path of the binary that was used to run the credential helper.

[minor-fixes]

Instructions say to put engflow_auth on $PATH, so IMO it's fair and more user-friendly to carry this assumption.

It's a bit less convenient for us, if we're working with dev builds - we have to know what we're doing there, instead of following the error message blindly. But I'd still prefer the simpler perceived UX for users.

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On second thought - maybe we can see if the current application is on $PATH, and display the full path if it isn't?

[jayconrod]

I think what @rogerhu is doing here is the best option: print os.Args[0].

If the user installed in PATH and invoked as engflow_auth, great, we report that.

If the user invoked with an absolute path (whether or not engflow_auth is in PATH), then we report that full path.

[rogerhu]

On second thought - maybe we can see if the current application is on $PATH, and display the full path if it isn't?

Addressing your concerns. Pushed some changes. =)

[rogerhu]

I think what @rogerhu is doing here is the best option: print os.Args[0].

If the user installed in PATH and invoked as engflow_auth, great, we report that.

If the user invoked with an absolute path (whether or not engflow_auth is in PATH), then we report that full path.

Ok, I'll keep it as is. =)