Checks for shared file modifications within a commit range

git-overlap.sh

#!/usr/bin/env bash
#
# Checks the configured commit range to determine which commits modify files
# that were modified in an earlier commit.
#
# Example:
#  Commit 1:
#    foo.txt
#    bar.txt
#  Commit 2:
#    bar.txt
#  Commit 3:
#   foo.txt
#  Commit 4:
#    foobar.txt
#
# Commit 2 will be considered dependent on Commit 1.
# Commit 3 will be considered dependent on Commit 1, but not 2.
# Commit 4 will not be considered to have any dependencies.
#
# This is a very shallow check which does not account for functional or thematic
# dependencies. It should be considered a starting point for further
# investigation.
#
# Usage:
#  git-overlap start_commit end_commit
#
# Example:
#  git-overlap develop feature/my-new-feature

set +x

declare -a COMMITS=($(git log --pretty='format:%h' ${1}..${2}))
declare -i LEN=${#COMMITS[@]}

indent() { sed 's/^/  /'; }

function compare_commit_files() {
  local PARENT_FILES=$(git show --name-only ${1} | tail -r | awk '1;/^$/{exit}' | awk 'NF' | sort)
  local CHILD_FILES=$(git show --name-only ${2} | tail -r | awk '1;/^$/{exit}' | awk 'NF' | sort)
  local MODIFIED=$(comm -12 <(echo "${PARENT_FILES}") <(echo "${CHILD_FILES}"))
  [[ "${MODIFIED}" ]]
}

echo "Checking the following commits for overlapping changes:"
echo
echo "  ${COMMITS[@]}"
echo
echo

for (( index = 0; index < $(($LEN-1)); index ++ )); do
  declare -a DEPENDS_ON=()
  CURRENT=${COMMITS[ $index ]}

  echo -n "Parent ${CURRENT} -> "

  for (( child_index = $(($index + 1)); child_index < $LEN; child_index ++ )); do
    CURRENT_CHILD=${COMMITS[$child_index]}
    echo -n "${CURRENT_CHILD} "

    compare_commit_files $CURRENT $CURRENT_CHILD
    if [[ $? -eq true ]]; then
      DEPENDS_ON+=("${CURRENT_CHILD}")
    fi
  done
  echo

  if [[ ${#DEPENDS_ON[@]} -gt 0 ]]; then
    echo
    echo "${CURRENT} shares changes with ${DEPENDS_ON[@]}" | indent
    echo
    for depend in ${DEPENDS_ON[@]}; do
      git log --format=%B -n 1 ${depend} | awk 'NF' | indent | indent
    done
    echo
  fi
done