Search a git branch log for revert commits, and output a csv file containing details of the revert commit, the commit that was reverted, and the time in seconds between the two.

git-revert-time

#!/usr/bin/env bash
set -eu -o pipefail

# Set default values for unset variables
: ${OUT_DIR:="${HOME}/tmp/git-revert-time"}
: ${REMOTE:='origin'}
: ${BRANCH:='master'}
: ${SINCE:='2020-01-01'}

echo "Output and temp files will be written to ${OUT_DIR}"
mkdir -p "${OUT_DIR}"

echo 'Fetch latest commits'
git fetch --quiet "${REMOTE}" "${BRANCH}"

echo 'Computing log'

git log "${REMOTE}/${BRANCH}" \
    --since "${SINCE}" \
    --extended-regexp \
    --grep  'This reverts commit [0-9a-f]{40}\.' \
    --format=format:'%H,%cI,%aI%n%B' -z \
    > "${OUT_DIR}/reverts_log"

echo 'Computing pre-fetch list'

echo 'commit_hash,revert_hash,revert_author_time' > "${OUT_DIR}/pre-fetch_list.csv"

cat "${OUT_DIR}/reverts_log" \
    | while IFS='' read -r -d $'\0' commit; do
          echo "${commit}" | (
              IFS=',' read -r -d $'\n' revert_hash revert_commit_time revert_author_time

              # Do a 2 step egrep rather than a lookahead (with --perl-regexp),
              # because macOS / BSD egrep doesn't support --perl-regexp.
              commit_hash="$(egrep -o -e 'This reverts commit [0-9a-f]{40}\.' \
                                | head -n1 \
                                | egrep -o -e '[0-9a-f]{40}')"
              echo "${commit_hash},${revert_hash},${revert_author_time}"
          )
      done >> "${OUT_DIR}/pre-fetch_list.csv"

echo 'Pre-fetching commits'

tail -n +2 "${OUT_DIR}/pre-fetch_list.csv" \
    | cut -d ',' -f 1 \
    | xargs git fetch --quiet "${REMOTE}"

echo 'Computing final output'

echo 'commit_hash,commit_author_time,revert_hash,revert_author_time,time_diff_secs' \
    > "${OUT_DIR}/reverts.csv"

tail -n +2 "${OUT_DIR}/pre-fetch_list.csv" \
    | while IFS=',' read -r commit_hash revert_hash revert_author_time; do
          # commit_author_time="$(git show ${commit_hash} --format=format:'%aI' --no-patch)"
          commit_author_time="$(git log -n 1 ${commit_hash} --format=format:'%aI' --no-patch)"

          commit_author_secs="$(date +%s -d "${commit_author_time}")"
          revert_author_secs="$(date +%s -d "${revert_author_time}")"
          time_diff_secs="$(( ${revert_author_secs} - ${commit_author_secs} ))"
          echo "${commit_hash},${commit_author_time},${revert_hash},${revert_author_time},${time_diff_secs}"
done >> "${OUT_DIR}/reverts.csv"

echo -e "\nDone! See final output in ${OUT_DIR}/reverts.csv"