Prevent pushing fixup, squash, and WIP commits to master.

pre-push

#!/bin/sh

# An example hook script to verify what is about to be pushed to master.  Called
# by "git push" after it has checked the remote status, but before anything has
# been pushed.  If this script exits with a non-zero status nothing will be
# pushed.
#
# This hook is called with the following parameters:
#
# $1 -- Name of the remote to which the push is being done
# $2 -- URL to which the push is being done
#
# If pushing without using a named remote those arguments will be equal.
#
# Information about the commits which are being pushed is supplied as lines to
# the standard input in the form:
#
#   <local ref> <local sha1> <remote ref> <remote sha1>
#
# This sample shows how to prevent push of commits where the log message starts
# with "WIP" (work in progress).

remote="$1"
url="$2"

z40=0000000000000000000000000000000000000000

IFS=' '
while read local_ref local_sha remote_ref remote_sha
do
	if [ "$remote_ref" != "refs/heads/master" ]
	then
        continue
	fi

	if [ "$local_sha" = $z40 ]
	then
		# Handle delete
		:
	else
		if [ "$remote_sha" = $z40 ]
		then
			# New branch, examine all commits
			range="$local_sha"
		else
			# Update to existing branch, examine new commits
			range="$remote_sha..$local_sha"
		fi

		# Check for WIP commit
		commit=`git rev-list -n 1 --regexp-ignore-case --grep '^WIP' "$range"`
		if [ -n "$commit" ]
		then
			echo "Found WIP commit in $local_ref, not pushing"
			exit 1
		fi
		commit=`git rev-list -n 1 --grep '^squash!' "$range"`
		if [ -n "$commit" ]
		then
			echo "Found squash! commit in $local_ref, not pushing"
			exit 1
		fi
		commit=`git rev-list -n 1 --regexp-ignore-case --grep '^fixup!' "$range"`
		if [ -n "$commit" ]
		then
			echo "Found fixup! commit in $local_ref, not pushing"
			exit 1
		fi
	fi
done

exit 0

Add this to your git hooks directory and make it executable. Before git pushes it will run this hook which can stop incomplete work being pushed.

---

You can create a shared hooks directory that will be used by all repositories on you system.

Place this file somewhere and then run git config --global core.hooksPath <path>.