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djeada merged 2 commits into from
Sep 29, 2025
Merged

Refactor commit date modifier to support multiple modes #23

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a0a35bd
Refactor commit date modifier to support multiple modes
djeada Sep 29, 2025
4a4f354
Update src/change_commit_date.sh
djeada Sep 29, 2025
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359 changes: 296 additions & 63 deletions src/change_commit_date.sh
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Original file line number Diff line number Diff line change
@@ -1,84 +1,317 @@
#!/usr/bin/env bash
set -euo pipefail

# Script Name: commit_date_modifier.sh
# Description: Modifies the date of the latest Git commit to a user-provided date
# Usage: commit_date_modifier.sh DD-MM-YYYY
# The date is in the format day-month-year
# Example: commit_date_modifier.sh 25-12-2022
# -----------------------------------------------------------------------------
# commit_date_tools.sh
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Copilot AI Sep 29, 2025

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The script filename in the comment doesn't match the actual filename 'change_commit_date.sh'. This should be updated to reflect the correct filename.

Copilot uses AI. Check for mistakes.
#
# Powerful Git commit-date tools:
# 1) amend-latest: set latest commit to a specific date/time
# 2) shift: shift ALL commits by hours/days
# 3) move: move ALL commits into day or night hours (randomized within window)
#
# Defaults:
# - Timezone offset: +0200 (UTC+2)
# - Day window: 09-18 (9am..6pm)
# - Night window: 20-23,00-05 (8pm..11pm and midnight..5am)
#
# Requirements: git, GNU date (Linux 'date' or macOS 'gdate' from coreutils)
#
# Examples:
# # 1) Set latest commit to specific day (random time) in UTC+2
# ./commit_date_tools.sh amend-latest --date 25-12-2022
#
# # 1b) Set latest commit to specific day & time with custom tz
# ./commit_date_tools.sh amend-latest --date 25-12-2022 --time 14:30 --tz +0530
#
# # 2) Shift entire history forward 7 hours
# ./commit_date_tools.sh shift --hours 7
#
# # 2b) Shift entire history back 2 days and 3 hours, timezone +0200
# ./commit_date_tools.sh shift --days -2 --hours -3 --tz +0200
#
# # 3) Move all commits into daytime (random hour in window)
# ./commit_date_tools.sh move --to day
#
# # 3b) Move to night hours with custom windows and timezone
# ./commit_date_tools.sh move --to night --night-window 21-23,00-04 --tz -0500
#
# After rewriting history:
# git push --force-with-lease
# -----------------------------------------------------------------------------

# Function: Returns absolute value of a number
abs() {
echo "${1#-}"
# ---------- Utilities ----------

# Pick GNU date (Linux: date, macOS: gdate)
DATE_BIN="$(command -v gdate || command -v date)"
if ! "$DATE_BIN" -d "@0" +%s >/dev/null 2>&1; then
echo "Error: GNU 'date' required. On macOS: brew install coreutils (use gdate)." >&2
exit 1
fi

require_git_repo() {
git rev-parse --git-dir >/dev/null 2>&1 || { echo "Not a git repo."; exit 1; }
}

# Function: Convert the input date into a weekday string
day_string_converter() {
local day=$1
local month=$2
local year=$3
# Parse "+HHMM" or "-HHMM" into seconds (supports half-hours like +0530)
tz_to_seconds() {
local tz="$1" sign hh mm secs
[[ "$tz" =~ ^[+-][0-9]{4}$ ]] || { echo "Invalid tz offset '$tz' (use +HHMM/-HHMM)"; exit 1; }
sign="${tz:0:1}"
hh=$((10#${tz:1:2}))
mm=$((10#${tz:3:2}))
secs=$((hh*3600 + mm*60))
if [[ "$sign" == "-" ]]; then secs=$((-secs)); fi
echo "$secs"
}

# Zeller's Congruence algorithm for calculating the day of the week
local a=$(( (14 - month) / 12 ))
local y=$(( year - a ))
local m=$(( month + (12 * a) - 2 ))
local d=$(( (day + y + (y / 4) - (y / 100) + (y / 400) + ((31 * m) / 12)) % 7 ))
# Random int in [min,max] inclusive
rand_int() {
local min=$1 max=$2
echo $(( min + RANDOM % (max - min + 1) ))
}

local days=("Sun" "Mon" "Tue" "Wed" "Thu" "Fri" "Sat")
# Build a space-separated list of allowed hours from a window spec like "09-18" or "20-23,00-05"
expand_windows_to_hours() {
local spec="$1" part start end h hours=()
IFS=',' read -ra PARTS <<< "$spec"
for part in "${PARTS[@]}"; do
[[ "$part" =~ ^([0-1][0-9]|2[0-3])\-([0-1][0-9]|2[0-3])$ ]] \
|| { echo "Invalid window '$part' (use HH-HH,HH-HH)"; exit 1; }
start="${part%-*}"; end="${part#*-}"
start=$((10#$start)); end=$((10#$end))
if (( start <= end )); then
for ((h=start; h<=end; h++)); do hours+=("$h"); done
else
# Wrap around midnight (e.g., 20-05)
for ((h=start; h<=23; h++)); do hours+=("$h"); done
for ((h=0; h<=end; h++)); do hours+=("$h"); done
fi
done
echo "${hours[*]}"
}

echo "${days[d]}"
# Turn Y-m-d H:M:S in the *local tz* into epoch seconds:
ymd_hms_to_epoch_in_tz() {
local y="$1" m="$2" d="$3" H="$4" M="$5" S="$6" tz="$7"
"$DATE_BIN" -d "${y}-${m}-${d} ${H}:${M}:${S} ${tz}" +%s
}

# Function: Convert numeric month into a month string
month_string_converter() {
local month_strs=("Jan" "Feb" "Mar" "Apr" "May" "Jun" "Jul" "Aug" "Sep" "Oct" "Nov" "Dec")
# ---------- Modes ----------

print_help() {
cat <<'EOF'
Usage:
commit_date_tools.sh <mode> [options]

Modes:
amend-latest Set the latest commit to a specific date/time.
shift Shift ALL commits by hours/days.
move Move ALL commits into day or night hours (randomized).

Common options:
--tz <+HHMM|-HHMM> Timezone offset to use when writing dates (default +0200).

amend-latest options:
--date DD-MM-YYYY Required (e.g., 25-12-2024)
--time HH:MM Optional (random if omitted)

echo "${month_strs[$1-1]}"
shift options:
--hours N Integer hours to shift (can be negative)
--days N Integer days to shift (can be negative)

move options:
--to day|night Required
--day-window HH-HH Default 09-18
--night-window HH-HH,HH-HH Default 20-23,00-05

Notes:
• This rewrites history (all branches & tags). Backup first.
• After running: git push --force-with-lease
EOF
}

# Function: Generate a random time string in the format HH:MM
random_time() {
printf -v time "%02d:%02d" $((RANDOM % 24)) $((RANDOM % 60))
echo "$time"
# ---------- Argument parsing ----------

MODE="${1:-}"
[[ -z "${MODE}" ]] && { print_help; exit 1; }
shift || true

TZ_OFFSET="+0200"
DATE_DDMMYYYY=""
TIME_HHMM=""
SHIFT_HOURS="0"
SHIFT_DAYS="0"
MOVE_TO=""
DAY_WINDOW="09-18"
NIGHT_WINDOW="20-23,00-05"

while (( "$#" )); do
case "$1" in
--tz) TZ_OFFSET="${2:?}"; shift 2;;
--date) DATE_DDMMYYYY="${2:?}"; shift 2;;
--time) TIME_HHMM="${2:?}"; shift 2;;
--hours) SHIFT_HOURS="${2:?}"; shift 2;;
--days) SHIFT_DAYS="${2:?}"; shift 2;;
--to) MOVE_TO="${2:?}"; shift 2;;
--day-window) DAY_WINDOW="${2:?}"; shift 2;;
--night-window) NIGHT_WINDOW="${2:?}"; shift 2;;
-h|--help) print_help; exit 0;;
*) echo "Unknown option: $1"; echo; print_help; exit 1;;
esac
done

# ---------- Validations ----------

require_git_repo
TZ_SECS="$(tz_to_seconds "$TZ_OFFSET")"

# ---------- Implementations ----------

amend_latest() {
[[ "$DATE_DDMMYYYY" =~ ^([0-2][0-9]|3[0-1])-([0][1-9]|1[0-2])-[0-9]{4}$ ]] \
|| { echo "Invalid --date. Use DD-MM-YYYY"; exit 1; }
IFS='-' read -r DD MM YYYY <<< "$DATE_DDMMYYYY"

if [[ -z "$TIME_HHMM" ]]; then
HH=$(rand_int 0 23)
MMm=$(rand_int 0 59)
printf -v TIME_HHMM "%02d:%02d" "$HH" "$MMm"
else
[[ "$TIME_HHMM" =~ ^([0-1][0-9]|2[0-3]):([0-5][0-9])$ ]] \
|| { echo "Invalid --time. Use HH:MM"; exit 1; }
fi

HH="${TIME_HHMM%:*}"
MI="${TIME_HHMM#*:}"
SS="00"

EPOCH="$("$DATE_BIN" -d "${YYYY}-${MM}-${DD} ${HH}:${MI}:${SS} ${TZ_OFFSET}" +%s)"

GIT_AUTHOR_DATE="${EPOCH} ${TZ_OFFSET}" \
GIT_COMMITTER_DATE="${EPOCH} ${TZ_OFFSET}" \
git commit --amend --no-edit

echo "✓ Amended latest commit date to ${YYYY}-${MM}-${DD} ${HH}:${MI}:${SS} ${TZ_OFFSET}"
}

# Function: Validate the input date format
validate_date() {
if [[ $1 =~ ^([1-9]|0[1-9]|[12][0-9]|3[01])-(0[1-9]|1[0-2])-([0-9]{4})$ ]]; then
IFS='-' read -r day month year <<< "$1"
# Check the date validity
if ! date -d"$month/$day/$year" >/dev/null 2>&1; then
echo "Invalid date: $1"
exit 1
fi
else
echo "Incorrect date format: $1. Expected format: DD-MM-YYYY"
exit 1
fi
shift_history() {
local shift_secs=$(( SHIFT_DAYS*86400 + SHIFT_HOURS*3600 ))
echo "Shifting ALL commits by ${SHIFT_DAYS} day(s) and ${SHIFT_HOURS} hour(s) [${shift_secs}s]; tz=${TZ_OFFSET}"
if [[ "$shift_secs" -eq 0 ]]; then
echo "Nothing to do (shift is zero)."; exit 0
fi

git filter-branch -f --tag-name-filter cat --env-filter "
shift_secs=${shift_secs}
tz='${TZ_OFFSET}'
to_epoch() { $DATE_BIN -d \"\$1\" +%s; }

a_ep=\$(to_epoch \"\$GIT_AUTHOR_DATE\"); c_ep=\$(to_epoch \"\$GIT_COMMITTER_DATE\")
a_new=\$((a_ep + shift_secs)); c_new=\$((c_ep + shift_secs))
export GIT_AUTHOR_DATE=\"\$a_new \$tz\"
export GIT_COMMITTER_DATE=\"\$c_new \$tz\"
" -- --branches --tags >/dev/null
echo "✓ Done. Remember to: git push --force-with-lease"
}

# Function: Main function to control the script flow
main() {
if [ $# -ne 1 ]; then
echo "Error: No arguments provided."
echo "Usage: commit_date_modifier.sh DD-MM-YYYY"
echo " The date is in the format day-month-year."
echo "Example: commit_date_modifier.sh 25-12-2022"
exit 1
fi
move_history() {
local target="$1"

local hours_list=""
if [[ "$target" == "day" ]]; then
hours_list="$(expand_windows_to_hours "$DAY_WINDOW")"
echo "Moving ALL commits into DAY hours [${DAY_WINDOW}] in tz=${TZ_OFFSET}"
else
hours_list="$(expand_windows_to_hours "$NIGHT_WINDOW")"
echo "Moving ALL commits into NIGHT hours [${NIGHT_WINDOW}] in tz=${TZ_OFFSET}"
fi

# Pack the hours list into a bash array initializer string
local hours_csv="${hours_list// /,}"

git filter-branch -f --tag-name-filter cat --env-filter "
tz='${TZ_OFFSET}'
tz_secs=$(tz_to_seconds "${TZ_OFFSET}")
" -- --branches --tags >/dev/null 2>&1 && true
Comment on lines +232 to +235
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Copilot AI Sep 29, 2025

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Running git filter-branch twice is inefficient and potentially problematic. The first filter-branch call appears incomplete and unnecessary since the actual logic is implemented in the second call.

Suggested change
git filter-branch -f --tag-name-filter cat --env-filter "
tz='${TZ_OFFSET}'
tz_secs=$(tz_to_seconds '${TZ_OFFSET}') # <- will be substituted by this script (not inside env-filter)
" -- --branches --tags >/dev/null 2>&1 && true

Copilot uses AI. Check for mistakes.

# We need the tz_to_seconds helper inside the filter; inject it plus logic:
git filter-branch -f --tag-name-filter cat --env-filter "
tz='${TZ_OFFSET}'
tz_to_seconds() {
local tz=\"\$1\" sign hh mm secs
[[ \"\$tz\" =~ ^[+-][0-9]{4}\$ ]] || { echo 'bad tz' >&2; exit 1; }
sign=\"\${tz:0:1}\"; hh=\$((10#\${tz:1:2})); mm=\$((10#\${tz:3:2}))
secs=\$((hh*3600 + mm*60)); [[ \"\$sign\" == '-' ]] && secs=\$((-secs))
echo \"\$secs\"
}

tz_secs=\$(tz_to_seconds \"\$tz\")
to_epoch() { $DATE_BIN -d \"\$1\" +%s; }
from_local_YmdHMS_to_epoch() { # args: Y M D H M S, interpret as LOCAL (tz offset), return UTC epoch
local Y=\"\$1\" Mo=\"\$2\" D=\"\$3\" H=\"\$4\" Mi=\"\$5\" S=\"\$6\"
$DATE_BIN -d \"\${Y}-\${Mo}-\${D} \${H}:\${Mi}:\${S} UTC\" +%s
}
Comment on lines +249 to +253
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Copilot AI Sep 29, 2025

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The from_local_YmdHMS_to_epoch function is defined but never used in the script. This creates unnecessary complexity and should be removed.

Copilot uses AI. Check for mistakes.

# Pick a random allowed hour (uniform)
pick_hour() {
local IFS=','; local raw='${hours_csv}'
read -ra H <<< \"\$raw\"
local count=\${#H[@]}
local idx=\$((RANDOM % count))
echo \${H[\$idx]}
}

# For each commit:
a_ep=\$(to_epoch \"\$GIT_AUTHOR_DATE\")
c_ep=\$(to_epoch \"\$GIT_COMMITTER_DATE\")

# Convert to 'local' by applying tz offset (so windows are in given tz)
a_local=\$((a_ep + tz_secs))
c_local=\$((c_ep + tz_secs))

# Extract local Y-m-d; choose random HH:MM:SS in allowed window
Y=\$($DATE_BIN -u -d @\$a_local +%Y)
Mo=\$($DATE_BIN -u -d @\$a_local +%m)
D=\$($DATE_BIN -u -d @\$a_local +%d)

H=\$(pick_hour)
Mi=\$((RANDOM % 60))
S=\$((RANDOM % 60))

new_local_epoch=\$($DATE_BIN -u -d \"\${Y}-\${Mo}-\${D} \${H}:\${Mi}:\${S}\" +%s)
a_new=\$((new_local_epoch - tz_secs))

# Mirror author -> committer with same new time on that commit's day
Yc=\$($DATE_BIN -u -d @\$c_local +%Y)
Moc=\$($DATE_BIN -u -d @\$c_local +%m)
Dc=\$($DATE_BIN -u -d @\$c_local +%d)
new_local_epoch_c=\$($DATE_BIN -u -d \"\${Yc}-\${Moc}-\${Dc} \${H}:\${Mi}:\${S}\" +%s)
c_new=\$((new_local_epoch_c - tz_secs))

export GIT_AUTHOR_DATE=\"\$a_new \$tz\"
export GIT_COMMITTER_DATE=\"\$c_new \$tz\"
" -- --branches --tags >/dev/null

local date="$1"
validate_date "$date"
IFS='-' read -r day month year <<< "$date"
local day_string
local month_string
local time_string
day_string=$(day_string_converter "$day" "$month" "$year")
month_string=$(month_string_converter "$month")
time_string=$(random_time)

GIT_COMMITTER_DATE="$day_string $month_string $day $time_string $year +0100" git commit --amend --no-edit --date "$day_string $month_string $day $time_string $year +0100"
echo "Commit date modified to $day_string $month_string $day $time_string $year"
echo "✓ Done. Remember to: git push --force-with-lease"
}

main "$@"
# ---------- Dispatch ----------

case "$MODE" in
amend-latest)
[[ -n "$DATE_DDMMYYYY" ]] || { echo "amend-latest requires --date DD-MM-YYYY"; exit 1; }
amend_latest
;;
shift)
shift_history
;;
move)
[[ "$MOVE_TO" =~ ^(day|night)$ ]] || { echo "move requires --to day|night"; exit 1; }
move_history "$MOVE_TO"
;;
*)
echo "Unknown mode: $MODE"
print_help
exit 1
;;
esac