Can I return a message from a python git pre-receive hook prefixed error: instead of remote:

Question

I have written a git pre-receive hook in python to abort the process if a user tries to push to a prohibited directory.

The function that does this takes a parameter of filepaths and iterates over them looking for the naughty dir, like this;

for filename in changed:
    pieces = filename.split('/')
    if(len(pieces) >3 and pieces[0] == 'application' and pieces[1] == 'modules' and pieces[3] == 'core'):
        # User is trying to push to application/modules/[MODULE_NAME]/core directory, they must be stopped!
        msg = 'You are pushing code that will be over-written by framework updates: ' + filename + '. THIS IS NOT ALLOWED!'
        print(msg)
        exit(1)

This works, and returns a message formatted like this;

remote: You are pushing code that will be overwritten..etc.

Which is followed by

error: failed to push some refs...etc.

What I would like to do however, is replace the print call and return the message as an error instead, so it reads;

error: You are pushing code will be overwritten...etc.

My reasoning is that I suspect different gui git clients will present errors differently (i.e. in red, with a pop-up, exclamation marks etc.) and they are more likely to be read by the person trying to push. Does anyone know how to do this please?

Answer 1

You can't, as git's hook handling code simply takes every string that comes back (on sideband channel 2, specifically; that's where hook output winds up) and sticks the word remote: in front of it (see recv_sideband() in sideband.c). You could get it to print remote: error: and cross fingers that the gui will recognize that as an error string, perhaps. :-)