Git Hammer

Git Hammer is a statistics tool for projects in git repositories. Its major feature is tracking the number of lines authored by each person for every commit, but it currently includes some other useful statistics as well, and the data that it collects could be used in multiple new ways as well.

Git Hammer is under active maintenance. New features appear when a need or desire for them exists. If Git Hammer lacks some feature you would like, all kinds of contributions are welcome, from simple feature suggestions to complete pull requests implementing the feature.

Setup

By default, Git Hammer stores the historical information from the repository in an SQLite database file in the current directory. If you wish to change this default, set the DATABASE_URL environment variable to a database URL according to the SQLAlchemy engine documentation. This database will be created if it does not already exist. Note that if you wish to use a database other than SQLite, you may need to install the appropriate Python module to connect to the database.

You will need Python 3, at least version 3.5. It is a good idea to set up a virtual environment, like this:

python3 -m venv venv
source venv/bin/activate

Run these commands wherever you want to run Git Hammer. If you only want to use Git Hammer, you can install it with pip:

pip install git-hammer

If you want to use the latest development version or contribute to Git Hammer development, you need to clone this repository and run

pip install -r requirements.txt

in the directory where you cloned Git Hammer (in this case you should create the virtual environment above in that directory as well). The rest of the commands below assume that one of these has been done.

Creating a Project

Now pick some git repository to run Git Hammer on. The examples below use a hypothetical project called "baffle". You should replace the name with your own.

python -m githammer init-project baffle ~/projects/baffle

This will create the database containing the project baffle from the repository directory (here ~/projects/baffle; replace that with the path to your repository). Git Hammer will print out a progress report while it goes through all the commits in the repository.

Usually, you want your main development branch to be checked out in the repository, and not change the checked-out branch when updating Git Hammer data. This makes the statistics more relevant for the whole development team.

When the repository gets new development, first update the code in the repository to the latest version, and then run

python -m githammer update-project baffle

This will process all the new commits that were not yet seen into the database.

If the repository is very old, with much history, you might not be interested in capturing all of it. init-project has the option --earliest-commit-date that provides a date so that commits prior to that date are not included. This would be used like

python -m githammer init-project baffle ~/projects/baffle --earliest-commit-date 2018-01-01

It is currently not possible to later add commits that were excluded by date when the repository was added.

Showing Statistics

After the project has been initialized and the repository added, you can show some information on it. First try out

python -m githammer summary baffle

This will print out three tables: The number of commits for each person, the number of lines of code written by each person in the head version, and the number of tests written by each person in the head version. This last is only printed if the repository configuration includes test recognition (see below).

There are a few graphs that Git Hammer can display. To see the types of supported graphs, enter

python -m githammer graph --help

The graphs are

Type	Description
line-count	Number of lines in the project over time
line-author-count	Same as above, except split per author
test-count	Number of tests in the project over time
test-author-count	Same as above, except split per author
day-of-week	A histogram showing the number of commits for each day of the week
time-of-day	A histogram showing the number of commits for each hour of the day

Configuring Sources and Tests

By default, Git Hammer assumes that every file in the repository is a source file and that there are no tests. This can be modified by creating a configuration file. The configuration file is JSON having some predefined keys:

{
  "sourceFiles": [
    "Sources/**/*.py",
    "Tests/**/*.py",
    ...
  ],
  "excludedSourceFiles": [
    "Sources/Contrib/**"
  ],
  "testFiles": [
    "Tests/**/*.py"
  ],
  "testLineRegex": "def test_"
}

Here, sourceFiles is a list of patterns that match the source files. Any file not matching one of these patterns is not considered by Git Hammer. If sourceFiles captures too many files, for instance autogenerated sources, excludedSourceFiles is a list of patterns that will not be considered source even if they match some sourceFiles pattern.

To include test counts, testFiles needs to be specified. This is again, a list of patterns matching files that contain tests (it is up to you if you wish to define this to mean unit tests, integration tests, UI tests, etc.). Git Hammer will look inside each of the test files. Any line matching the Python regular expression testLineRegex is counted as one test. So testLineRegex should typically match whatever acts as the header of a test. Here, it is the definition of a function named starting with test_. Other projects, and especially other languages, will have different conventions.

All the file name patterns above (sourceFiles, excludedSourceFiles, testFiles) are glob patterns as defined by the globber library.

The configuration file can be given as an option to the init-project command:

python -m githammer init-project baffle ~/projects/baffle --configuration ./baffle-config.json

If the --configuration option is not given, but the repository contains a file named git-hammer-config.json, this file will be read as the configuration. This way you can keep the Git Hammer configuration for a repository in that repository.

Note: The configuration file path, as well as the repository path, will be stored in the database, so they should not be moved. If the configuration changes, data that was already in the database will not be reprocessed with the new configuration.

There is also a command to check what are the effects of a configuration. Run

python -m githammer list-sources ~/projects/baffle --configuration ./baffle-config.json

to print out a list of all files considered source or test files, and for each test file, the lines considered to be tests. A missing --configuration option is treated in the same way as with init-project above.

A partial output of the list-sources command on the Git Hammer repository looks like this:

S: githammer/dbtypes.py
S: githammer/frequency.py
S: githammer/hammer.py
T: tests/__init__.py
T: tests/check_regression.py
T: tests/hammer_test.py
T: tests/test_init.py
|---    def test_plain_init_does_not_create_database(self):
|---    def test_update_fails_when_database_not_created(self):

Source files are marked with S, test files with T, and after each test file, its test lines are printed indented with |---.

Multi-Repository Projects

Sometimes, a team works on multiple repositories that all still belong to the same project. For instance, a piece of functionality may be better to split off into a library in an independent repository. Git Hammer supports such projects by not limiting the project data to a single repository.

To add another repository to an existing project, just use add-repository:

python -m githammer add-repository baffle ~/projects/baffle-common

This will process the new repository, adding it to the project database. After this, any summary information will include data from all repositories of the project. Like init-project, add-repository also accepts the --configuration and --earliest-commit-date options with the same semantics for the added repository.

Database Migrations

If you update Git Hammer, it is possible that the database schema is updated in the new version. This means that you will need to migrate any existing databases to the latest version. Migration is performed by running

HAMMER_DATABASE_URL=<URL of database to migrate> alembic upgrade head

(If you haven't installed Git Hammer with pip, run this command in the project directory and add PYTHONPATH=. at the beginning.)

It is safe to run this even if the database schema has not changed in the update, so there is no need to try and figure that out before running the migration.

License

Git Hammer is licensed under the Apache Software License, version 2.0. See the LICENSE file for precise license terms and conditions.