git pre-commit hook for setting CircleCI badge for current branch

gistfile1.txt

#!/usr/bin/python
"""
Referencing current branch in github readme.md[1]

This pre-commit hook[2] updates the README.md file's
CircleCI badge with the current branch. Gist at[4].

[1] http://stackoverflow.com/questions/18673694/referencing-current-branch-in-github-readme-md
[2] http://www.git-scm.com/book/en/v2/Customizing-Git-Git-Hooks
[3] https://circleci.com/docs/1.0/status-badges/
[4] https://gist.github.com/dandye/dfe0870a6a1151c89ed9
"""
import subprocess

# Hard-Coded for your repo (ToDo: get from remote?)
GITHUB_ORGANIZATION="github org or user"
REPO="repo"
CIRCLECI_ACCESS_TOKEN=""

print "Starting pre-commit hook..."

BRANCH=subprocess.check_output(["git",
                                "rev-parse",
                                "--abbrev-ref",
                                "HEAD"]).strip()

# String with hard-coded values
# See Embedding Status Images[3] for alternate formats (private repos, svg, etc)

#  [![CircleCI](https://circleci.com/gh/user/repo/tree/master.svg?style=shield
#  &circle-token=123456789)](https://circleci.com/gh/user/repo/tree/master)

# Output String with Variable substitution
circle="[![CircleCI](https://circleci.com/gh/" \
       "{GITHUB_ORGANIZATION}/{REPO}/tree/" \
       "branch={BRANCH}.svg?style=shield&circle-token={CIRCLECI_ACCESS_TOKEN})" \
       "(https://circleci.com/gh/{GITHUB_ORGANIZATION}/{REPO}/tree/{BRANCH})][circle]\n".format(BRANCH=BRANCH,
                                            GITHUB_ORGANIZATION=GITHUB_ORGANIZATION,
                                            REPO=REPO,
                                            CIRCLECI_ACCESS_TOKEN=CIRCLECI_ACCESS_TOKEN)

sentinal_str="[![Build Status]"

readmelines=open("README.md").readlines()
with open("README.md", "w") as fh:
    for aline in readmelines:
        if sentinal_str in aline and travis != aline:
            print "Replacing:\n\t{aline}\nwith:\n\t{travis}".format(
                   aline=aline,
                   travis=travis)
            fh.write(travis)
        else:
            fh.write(aline)

subprocess.check_output(["git", "add", "README.md" ])

print "pre-commit hook complete."