prepare-commit-msg

#!/bin/sh

# https://github.com/thisdougb/git-time-hooks
#
# This hook runs after the partner commit-msg hook. It works out
# the age of the merging branch, and adds that as a line in the
# merge commit message.
#
# The echo statements are mostly commented out, but can be enabled
# for debug purposes.

HOOKNAME=prepare-commit-msg

COMMIT_MSG_FILE=$1
COMMIT_SOURCE=$2
SHA1=$3

case "$COMMIT_SOURCE" in
    message)
        # ignore a regular commit
        exit 0 ;;

    merge)
        #echo "[$HOOKNAME] detect merge commit"

        # a merge commit uses the MERGE_MSG file as the commit message template,
        # initiall it contains the merging branch name on the first line.
        COMMIT_MSG_FILE=".git/MERGE_MSG" 
        MERGED_BRANCH=$(head -1 "${COMMIT_MSG_FILE}" \
            | sed "s/Merge branch '\(.*\)'.*/\1/g") ;;

    squash)
        #echo "[$HOOKNAME] detect squash commit"

        # the commit-msg hook should have added branched_created line per commit,
        # and that contains the merging branch name.
        MERGED_BRANCH=$(cat .git/SQUASH_MSG \
            | grep branch_created \
            | awk '{print $2}' \
            | sort \
            | uniq \
            | head -1) ;;
    *)
        # print a warning that there's a commit source we haven't catered for.
        echo "[$HOOKNAME] unknown commit source: $COMMIT_SOURCE"
        exit 0 ;;
esac

# list commits that were merged feature branch, by comparing with remote.
CURRENT_REMOTE=$(git rev-parse --abbrev-ref --symbolic-full-name @{u})
CURRENT_BRANCH=$(git rev-parse --abbrev-ref HEAD)

# double check and exit to avoid mess
if [ "$MERGED_BRANCH" = "" ]; then
  #echo [$HOOKNAME] did not detect the merged branch
  exit
fi;

#echo "[$HOOKNAME] detected merged branch: $MERGED_BRANCH."

# find oldest timestamp, because checkout time is local to user committing,
# Alice may have started working on her copy of the branch before Bob starts
# on his.
OLDEST_BRANCH_TIMESTAMP=$(git log "${CURRENT_BRANCH}..${MERGED_BRANCH}" \
    | grep "time_branch_created $MERGED_BRANCH" \
    | grep -v "$CURRENT_BRANCH" \
    | awk '{print $3}' \
    | sort \
    | head -1)

if [ "$OLDEST_BRANCH_TIMESTAMP" = "" ]; then
    exit
fi;

NOW=$(date +%s)
BRANCH_AGE=$((NOW-OLDEST_BRANCH_TIMESTAMP))

BRANCH_AGE_MSG=$(printf 'Time spent on %s: %dd:%dh:%dm secs=%d' \
    $MERGED_BRANCH \
    $((BRANCH_AGE/86400)) \
    $((BRANCH_AGE%86400/3600)) \
    $((BRANCH_AGE%3600/60)) \
    $BRANCH_AGE)

echo >> "$COMMIT_MSG_FILE"
echo "$BRANCH_AGE_MSG" >> "$COMMIT_MSG_FILE"