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Git hook scripts

What is it

A set of configurable git hooks and checks.

Upon committing code, the pre-commit hook runs configured checks against the files to be committed and rejects the commit if any of the checks turned on fail.



Install using pip::

pip install captainhook

You can then install the hooks using::

captainhook install

from within any git repo, and the pre-commit hook will be installed.

Running without commiting

You can perform a run against all your code base using::

captainhook run

Setting Up

To turn a check on or off, create a tox.ini or setup.cfg file (tox.ini is used for all further examples) in the base directory of your project with a captainhook section.



flake8, pdb and python3 checks default to being on.

Checks can also be passed arguments from the config file. This is done with the following notation::

<check_name>=<status>;<string to be passed through>

Currently checks can only be passed a single argument and must do the parsing of that themselves.

flake8 obeys the configuration as per the flake8 docs <>_ but any path-related options will need to use wildcard patterns (e.g. exclude=*/migrations/* instead of exclude=migrations).

To avoid being checked at all, you can commit using the --no-verify flag::

git commit -a --no-verify


Currently supported checks are

  • block_branch: A branch blacklist; will reject commits if the active branch is in the list.

  • flake8: Runs flake8_ on staged files (checks for PEP 8 compliance and syntax errors).

  • pytest: Runs pytest_ in repository directory.

  • pytest-cov: Runs pytest-cov_ in repository directory. You can specify level of threshold in tox.ini as number from 0 to 100.

  • pylint: Runs pylint_ on staged files. You can specify level of threshold in tox.ini as number from 0 to 10.

  • pylint_docstrings: Runs pylint_ to check only docstrings on staged files. You can specify level of threshold in tox.ini as number from 0 to 10.

  • frosted: Runs frosted_ on staged files (checks for Python syntax errors).

  • grep: Runs a single grep command on staged files, rejecting the commit if the value being searched is found. Options are passed to grep verbatim. Only one grep command may be specified.

  • isort: Runs isort_ on staged files (checks for clean Python imports according to PEP 8 and PEP 328).

  • merge_marks: Rejects the commit if there are any unresolved merge marks in staged files.

  • pdb: Rejects the commit if there are any uncommented import pdb; pdb.set_trace() statements in staged files.

  • python3: Rejects the commit if staged files are not Python 3 compatible. Expects python3 and 2to3-2.7 to be in the current shell PATH.


You only see output for checks that fail, otherwise silence.

Example output upon a rejected commit::

Checking python3
--- captainhook/   (original)
+++ captainhook/   (refactored)
@@ -66,7 +66,7 @@
     "Check there are changes to stash"
     return bool(bash('git diff'))

-print 'a'
Checking flake8
=============================================================================== F401 'importlib' imported but unused E302 expected 2 blank lines, found 1 E501 line too long (89 > 79 characters)
Rejecting commit


You can add your own check to your git env quite easily.

Simply add a module to .git/hooks/checkers with a run() method defined.

The method should return the error string on faillure, or a False like object on success.

For example::

$ cat .git/hooks/checkers/
DEFAULT = 'on'
def run():
    return "NOT A CHANCE"

This will block all commits if enabled.

A checker can set the following variables:

DEFAULT: used to determine the check is assumed "on" or "off". This value is only used if tox.ini has not been used to override it. The default DEFAULT is off.

CHECK_NAME: To override the display name of the module.

REQUIRED_FILES: Files that, if present, should be included in the copy to the temp directoy before analysis takes place.


I'm interested in hearing feedback - positive or negative - about this.

Please make yourself at home, create issues if you've got problems with existing behaviour, or suggestions for future improvements or anything else.

You can reach me on twitter @couperalex.


Running on its own will by default create copies of the files to be committed which you probably don't want when testing a new check.

You can run the script against all your code base using::

python captainhook/ --all


There are behavioural feature tests (based on behave) found in the features directory.

New checks should be accompanied by a corresponding behavioural test example.

To run the behavioural tests:

$ behave

To run all other tests:

$ nosetests

Ensure that you've installed test-requirements.txt.