[FS#361] git: add pre-receive hook to reject commits without SoB line

[LEDE Bugs]

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FS#361 - git: add pre-receive hook to reject commits without SoB line
User who did this: Stijn Tintel (stintel)
Task details edited:
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I recently pushed a commit without Signed-off-by. Looking at the git history, this happened before.
To avoid this in the future, add a pre-receive that checks for signed-off-by line, and rejects the push when it's not found.

Here is some (ugly) example python code that does this, and even goes 1 step further: it rejects the push if there is any commit that does not contain a SoB for the commit author. I think it makes sense to enforce this, it came up in https://github.com/lede-project/source/pull/592#issuecomment-265760007 .


#!/usr/bin/env python

import os, re, subprocess, sys

author = ""
for line in sys.stdin:
    (base, commit, ref) = line.strip().split()
    crange = '{}..{}'.format(base, commit)
    commits = subprocess.Popen(['git', 'log', '--format=%H', crange],stdout=subprocess.PIPE)
    for commit in iter(commits.stdout.readline, ''):
        msg = subprocess.Popen(['git', 'log', '-n 1', commit.strip()],stdout=subprocess.PIPE)
        found_sob = False
        for line in iter(msg.stdout.readline, ''):
            if line.startswith('Author: '):
                author = re.sub('^Author: ', '', line)
                continue
            if line.find('Signed-off-by: '):
                sob = re.sub('.*Signed-off-by: ', '', line)
                if sob == author:
                    found_sob = True
        if found_sob:
            continue
        else:
            print('No SoB line for author in commit {}'.format(commit))
            sys.exit(1)


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https://bugs.lede-project.org/index.php?do=details&task_id=361