Append a "Resolves: {tracker}#{ticket-id}" to commit messages based on branch names

prepare-commit-msg

#!/usr/bin/python
"""
This is a prepare-commit-msg hook that fill append commit messages with::

    Resolves: {TRACKER}#{TICKET-ID}

For example a RedHat BZ 0001 would look like::

    Correct the syntax error

    Signed-off-by: Alfredo Deza <adeza@redhat.com>

    Resolves: rhbz#0001

The requirement is to branch with the right identifier. For the above example
the branch name would need to be: rhbz-0001

This hook will split on `-` and use all lower casing to transform the branch
into the "Resolves" line.

Copy this file to $GITREPOSITORY/.git/hooks/prepare-commit-msg
and mark it executable.
"""
import subprocess
import sys
import os


def which(executable):
    locations = (
        '/usr/local/bin',
        '/bin',
        '/usr/bin',
        '/usr/local/sbin',
        '/usr/sbin',
        '/sbin',
    )

    for location in locations:
        executable_path = os.path.join(location, executable)
        if os.path.exists(executable_path):
            return executable_path

GIT = which('git')


def branch_name():
    try:
        name = subprocess.check_output(
            [GIT, "symbolic-ref", "HEAD"],
            stderr=subprocess.STDOUT)
    except Exception as err:
        if 'fatal: ref HEAD is not a symbolic ref' in err.output:
            # we are in a rebase or detached head state
            return ''
    # This looks like: refs/heads/12345678/my-cool-feature
    # if we ever get a branch that has '/' in it we are going to have
    # some issues.
    return name.split('/')[-1]
    parts = name.split('/')
    if len(parts) != 4:
        raise ValueError("Branch name has '/' in it which is not allowed")
    branch = parts[-1]
    return branch


def prepend_commit_msg(branch):
    """Prepend the commit message with `text`"""
    msgfile = sys.argv[1]
    with open(msgfile) as f:
        contents = f.read()

    if not branch:
        return contents

    try:
        prefix, ticket_id = branch.split('-')
        ticket_id = int(ticket_id)
    except ValueError:
        # We used to raise here, but if cherry-picking to a different branch
        # that doesn't comply it would break preventing the cherry-pick. So we
        # print out the warning, but end up returning the contents.
        print 'skipping commit msg change: Branch name "%s" does not follow required format: {tracker}-{ID}' % branch  # NOQA
        return contents

    if prefix == 'wip':
        # Skip "wip" branches, ie "work in progress"
        return contents

    resolves_line = "\nResolves: %s#%s" % (prefix.lower(), ticket_id)

    with open(msgfile, 'a') as f:
        # Don't append if it's already there
        if resolves_line not in contents:
            f.write(resolves_line)


def main():
    branch = branch_name().strip().strip('\n')
    prepend_commit_msg(branch)

if __name__ == '__main__':
    main()

Had a SyntaxError: Missing parentheses in call to 'print' when running downstream-cherry-pick in my Fedora 29 py3 environment, and fixed it with futurize -w0 prepare-commit-msg (trivial fix though):

--- .git/hooks/prepare-commit-msg	(original)
+++ .git/hooks/prepare-commit-msg	(refactored)
@@ -21,6 +21,7 @@
 Copy this file to $GITREPOSITORY/.git/hooks/prepare-commit-msg
 and mark it executable.
 """
+from __future__ import print_function
 import subprocess
 import sys
 import os
@@ -80,7 +81,7 @@
         # We used to raise here, but if cherry-picking to a different branch
         # that doesn't comply it would break preventing the cherry-pick. So we
         # print out the warning, but end up returning the contents.
-        print 'skipping commit msg change: Branch name "%s" does not follow required format: {tracker}-{ID}' % branch  # NOQA
+        print('skipping commit msg change: Branch name "%s" does not follow required format: {tracker}-{ID}' % branch)  # NOQA
         return contents
 
     if prefix == 'wip':

Can you revise this gist?

Additionally, decode() is required. These 2 things fix the py2-3 compatibility issues:

        name = subprocess.check_output(
            [GIT, "symbolic-ref", "HEAD"],
            stderr=subprocess.STDOUT)
+        if isinstance(name, bytes):
+          name = name.decode()

This probably can't be a gist anymore and should be an actual repository. Will make some updates to this. Thanks for the hints

@alfredodeza what do you think about merging this into https://github.com/red-hat-storage/downstream-cherry-picker ?

red-hat-storage/downstream-cherry-picker#23