dcover

#!/usr/bin/env bash
# dcover checks the coverage impact of merging the current Go monorepo branch
# into main.
#
# Uses colordiff: https://formulae.brew.sh/formula/colordiff
#
# Example:
#   git checkout featurebranch
#   dcover

set -e

tmp_dir=$(mktemp -d -t dcover)

# Get feature (current) branch name.
head=$(git rev-parse --abbrev-ref HEAD)
# Get main branch name.
main=$(mainbranch)

if [ "$head" = "$main" ]; then
  blog error "mainbranch returns $main; run dcover on a feature branch."
  exit
fi

# Profile main branch.
blog info "Profiling $main..."
git checkout "$main"
go test -coverprofile "$tmp_dir/main.out" ./...
mainCover=$(go tool cover -func="$tmp_dir/main.out" | tr -s '\t')

# Profile feature branch.
blog info "Profiling $head..."
git checkout "$head"
go test -coverprofile "$tmp_dir/branch.out" ./...
branchCover=$(go tool cover -func="$tmp_dir/branch.out" | tr -s '\t')

# An improved version would iterate over the tabular data and output comparisons
# package-by-package.

echo # Spacing.
blog info "Coverage impact of $head:"
colordiff --ignore-space-change <(echo "$mainCover") <(echo "$branchCover")

rm -rf "$tmp_dir"