prcost

prcost

Calculate the real-world cost of GitHub pull requests with detailed breakdowns of author effort, participant contributions, and delay costs.

Installation

go install github.com/codeGROOVE-dev/prcost/cmd/prcost@latest

Or build from source:

git clone https://github.com/codeGROOVE-dev/prcost
cd prcost
go build -o prcost ./cmd/prcost

Usage

prcost https://github.com/owner/repo/pull/123
prcost --format json https://github.com/owner/repo/pull/123
prcost --salary 300000 https://github.com/owner/repo/pull/123

Cost Model

This model is based on early research combining COCOMO II effort estimation with session-based time tracking. Individual PR estimates may be under or over-estimated, particularly for delay costs. The recommendation is to use this model across a large pool of PRs and rely on the law of averages for meaningful insights.

Author Costs

Code Cost: Writing effort estimated using COCOMO II: Effort = 2.94 × (KLOC)^1.0997. Minimum 20 minutes.

Code Context Switching: Cognitive overhead during code writing: COCOMO hours × 0.2 × sqrt(KLOC). Based on Microsoft interruption research (Czerwinski et al., 2004).

GitHub Time: Session-based calculation for GitHub interactions (commits, comments).

GitHub Context Switching: 20 minutes to context in, 20 minutes to context out per session.

Participant Costs

Review Cost: COCOMO II estimation applied to review comments.

GitHub Time: Session-based calculation for GitHub interactions.

GitHub Context Switching: Same 20-minute in/out costs per session.

Delay Costs

Project Delay (20%): Opportunity cost of blocked engineer time: hourly_rate × duration_hours × 0.20. Capped at 2 weeks after the last event, with an absolute maximum of 90 days.

Code Updates: Rework cost from code drift. Probability-based formula: drift = 1 - (0.96)^(days/7), modeling the cumulative probability that code becomes stale with 4% weekly churn. Applies to PRs open 3+ days, capped at 90 days (~41% max drift). Based on Windows Vista analysis (Nagappan et al., Microsoft Research, 2008).

Future GitHub: Cost for 3 future events (push, review, merge) with full context switching.

Session-Based Time Tracking

Events within 60 minutes are grouped into sessions to model real work patterns. This preserves flow state during continuous work and applies context switching costs only when work is interrupted.

Example (three events 5 min apart, one session):

• Event 1: 20 (in) + 20 (event) + 5 (gap) = 45 min
• Event 2: 5 (gap) + 20 (event) + 5 (gap) = 30 min
• Event 3: 5 (gap) + 20 (event) + 20 (out) = 45 min
• Total: 120 minutes

Example (two events 90 min apart, two sessions):

• Event 1: 20 + 20 + 20 = 60 min
• Event 2: 20 + 20 + 20 = 60 min
• Total: 120 minutes

License

Apache 2.0