Git Contributor Turnover Calculator

Hacked together bash script to calculate contributor turnover on git projects. Generates a CSV file with the dates of the first and last commits by each ex-contributor to a git repo (anyone who hasn't committed in the last 90 days), along with the difference between those dates in days. Also outputs an overall average for the repo.

Prerequisites

• Bash 4.0.0 or later (uses associative arrays)
• Git (version 2.x)
• yq (version 4.x)

Manual Preparation

Because engineers are tricksy and like to change the email and name in their local git config at random intervals - and therefore any analysis that doesn't take account of that is massively unreliable - this script depends on a human first manually putting together a yaml file like this:

emails:
  [email protected]: Joe Bloggs
  [email protected]: Joe Bloggs
  [email protected]: Jane Doe
  [email protected]: Jane Doe
names:
  Joe Bloggs: Joe Bloggs
  jd: Jane Doe
  Jane: Jane Doe

This is a mapping of the names and email addresses that appear in a git commit to a person's real name (or any other unique identifier - if you're pretty sure names/emails relate to the same person, it's better to map them to something than nothing). When trying to identify a contributor, the script first checks to see if their committer email maps to an email in the yaml config. If it doesn't, the script then checks to see if the committer's name maps. If neither do, we skip that contributor and they're excluded from the average turnover we calculate at the end.

You can generate a template like the above with the committer emails and names for your repo, with all values set to null, by running the following (the output path is optional - if unspecified the current directory will be used):

$ ./generate-template.sh REPO_PATH [OUTPUT PATH]

Created a template containing 152 emails and 178 names at ~/Workspace/git_contributors.yaml

Running the Script

Execute the script from anywhere, passing either an absolute path to your repo, or one relative to your current working directory.

$ ./git_contributor_commit_days_calculator.sh REPO_PATH [CONFIG_PATH] [OUTPUT_PATH]

Example:

$ ./git_contributor_commit_days_calculator.sh ~/Workspace/big/repo ~/Documents/git_contributors.yaml ~/Documents/git_contributors.csv

grabbing all unique emails from git log...
found 152 unique emails in git log, and 127 emails and 118 names that a nice human has configured for me in ~/Documents/git_contributors.yaml
using an excruciatingly inefficient technique to map committer email addresses and names to known contributors in ~/Documents/git_contributors.yaml and calculating first and last commit dates...
calculating total commit days for each contributor...
Unable to identify 14 contributors :-(
Ignored 22 committers who have committed in the last 90 days
Average commit days: 430
Total commit days: 24953
Total contributors: 58
Output CSV: ~/Documents/git_contributors.csv

The script also takes two optional arguments: paths to your YAML configuration file and the path where you'd like the script to generate its output CSV file. If not provided, the default names are git_contributors.yaml and git_contributors.csv, and it's assumed both should be in your current working directory.

The generated CSV has one row per identified contributor and four columns: Name, First Commit, Last Commit, and Commit Days