Check git rename detection before merging main into a feature branch

summarize-renames.sh

#!/usr/bin/env bash
set -euo pipefail

if [[ $# -ne 2 ]]; then
  echo "Usage: $(basename "$0") <feature-branch> <rename-threshold-0-100>" >&2
  exit 1
fi

FEATURE_BRANCH=$1
THRESHOLD=$2
MAIN_BRANCH=${MAIN_BRANCH:-main}

if ! [[ $THRESHOLD =~ ^[0-9]+$ ]] || (( THRESHOLD < 0 || THRESHOLD > 100 )); then
  echo "Rename threshold must be an integer between 0 and 100." >&2
  exit 1
fi

if ! git rev-parse --is-inside-work-tree >/dev/null 2>&1; then
  echo "This script must be run inside a Git repository." >&2
  exit 1
fi

resolve_ref() {
  local ref=$1
  if git rev-parse --verify --quiet "$ref" >/dev/null 2>&1; then
    printf '%s\n' "$ref"
  elif git rev-parse --verify --quiet "origin/$ref" >/dev/null 2>&1; then
    printf 'origin/%s\n' "$ref"
  else
    return 1
  fi
}

MAIN_REF=$(resolve_ref "$MAIN_BRANCH") || {
  echo "Cannot find branch or ref '$MAIN_BRANCH'." >&2
  exit 1
}
FEATURE_REF=$(resolve_ref "$FEATURE_BRANCH") || {
  echo "Cannot find branch or ref '$FEATURE_BRANCH'." >&2
  exit 1
}

MERGE_BASE=$(git merge-base "$MAIN_REF" "$FEATURE_REF") || {
  echo "Unable to determine merge base between $MAIN_REF and $FEATURE_REF." >&2
  exit 1
}

if [[ -t 1 && -z "${NO_COLOR:-}" ]]; then
  COLOR_RESET=$'\033[0m'
  COLOR_FILE=$'\033[1;36m'
  COLOR_FEATURE=$'\033[1;34m'
  COLOR_MAIN=$'\033[1;32m'
else
  COLOR_RESET=''
  COLOR_FILE=''
  COLOR_FEATURE=''
  COLOR_MAIN=''
fi

collect_renames() {
  local from_commit=$1
  local to_commit=$2
  git diff --find-renames="$THRESHOLD" --name-status "$from_commit" "$to_commit" |
    while IFS=$'\t' read -r status from_path to_path; do
      [[ $status == R* ]] || continue
      local score=${status#R}
      printf '%s\t%s\t%s\n' "$score" "$from_path" "$to_path"
    done
}

collect_modifications() {
  local from_commit=$1
  local to_commit=$2
  git diff --name-status "$from_commit" "$to_commit" |
    while IFS=$'\t' read -r status path _; do
      [[ $status == M* ]] || continue
      printf '%s\n' "$path"
    done
}

branch_renames=()
while IFS= read -r entry; do
  [[ -z $entry ]] && continue
  branch_renames+=("$entry")
done < <(collect_renames "$MERGE_BASE" "$FEATURE_REF")

main_renames=()
while IFS= read -r entry; do
  [[ -z $entry ]] && continue
  main_renames+=("$entry")
done < <(collect_renames "$MERGE_BASE" "$MAIN_REF")

branch_mods=()
while IFS= read -r path; do
  [[ -z $path ]] && continue
  branch_mods+=("$path")
done < <(collect_modifications "$MERGE_BASE" "$FEATURE_REF")

main_mods=()
while IFS= read -r path; do
  [[ -z $path ]] && continue
  main_mods+=("$path")
done < <(collect_modifications "$MERGE_BASE" "$MAIN_REF")

list_contains() {
  local target=$1
  shift
  local item
  for item in "$@"; do
    [[ $item == "$target" ]] && return 0
  done
  return 1
}

colorize_path() {
  local path=$1
  if [[ -n $COLOR_FILE ]]; then
    printf '%s%s%s' "$COLOR_FILE" "$path" "$COLOR_RESET"
  else
    printf '%s' "$path"
  fi
}

colorize_branch() {
  local branch=$1
  if [[ -n $COLOR_FEATURE && $branch == "$FEATURE_REF" ]]; then
    printf '%s%s%s' "$COLOR_FEATURE" "$branch" "$COLOR_RESET"
  elif [[ -n $COLOR_MAIN && $branch == "$MAIN_REF" ]]; then
    printf '%s%s%s' "$COLOR_MAIN" "$branch" "$COLOR_RESET"
  else
    printf '%s' "$branch"
  fi
}

print_section() {
  local title=$1
  shift
  echo "$title"
  if (( $# == 0 )); then
    echo "  (none)"
    return
  fi
  local entry
  for entry in "$@"; do
    IFS=$'\t' read -r score from_path to_path <<<"$entry"
    printf '  %s -> %s (similarity %s%%)\n' "$from_path" "$to_path" "$score"
  done
}

print_section "Renames/moves unique to ${FEATURE_REF}:" "${branch_renames[@]}"

if (( ${#main_renames[@]} )); then
  print_section "Renames/moves unique to ${MAIN_REF}:" "${main_renames[@]}"
fi

potential_conflicts=()

if (( ${#main_renames[@]} )); then
  for entry in "${branch_renames[@]}"; do
    IFS=$'\t' read -r score from_path to_path <<<"$entry"
    if list_contains "$from_path" "${main_mods[@]}"; then
      potential_conflicts+=("feature|$from_path|$to_path|$MAIN_REF")
    fi
  done
fi

if (( ${#main_renames[@]} )); then
  for entry in "${main_renames[@]}"; do
    IFS=$'\t' read -r score from_path to_path <<<"$entry"
    if list_contains "$from_path" "${branch_mods[@]}"; then
      potential_conflicts+=("main|$from_path|$to_path|$FEATURE_REF")
    fi
  done
fi

echo "Potential rename/modify conflicts:"
if (( ${#potential_conflicts[@]} == 0 )); then
  echo "  (none)"
else
  for conflict in "${potential_conflicts[@]}"; do
    IFS='|' read -r side from_path to_path other_ref <<<"$conflict"
    colored_from=$(colorize_path "$from_path")
    colored_to=$(colorize_path "$to_path")
    other_branch=$(colorize_branch "$other_ref")
    if [[ $side == feature ]]; then
      rename_branch=$(colorize_branch "$FEATURE_REF")
    else
      rename_branch=$(colorize_branch "$MAIN_REF")
    fi
    printf '  %s renamed to %s on %s; modified on %s\n' "$colored_from" "$colored_to" "$rename_branch" "$other_branch"
  done
fi