# Small git tools to take authorship from LLM work

> Source: <https://gist.github.com/alganet/2437625c4dc7c8f44ccf19aed2cfc996>
> Published: 2026-07-15 14:54:43+00:00

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#!/usr/bin/env bash |
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# |
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# git_reauthor.sh <back_until_sha_inclusive> <committer_name_email> <coauthored_by_name_email> |
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# |
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# Rewrite the identity (author AND committer name/email) of every commit from |
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# <back_until_sha_inclusive> up to HEAD, and fix up the Co-Authored-By trailer. |
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# |
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# Arguments 2 and 3 are optional: |
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# * no <committer_name_email> -> use the current git config user.name/email |
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# as the identity (and, since arg 3 is then also absent, strip co-authors). |
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# * no <coauthored_by_name_email> -> strip every Co-Authored-By line from the |
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# commit messages. |
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# * <coauthored_by_name_email> present -> replace any existing Co-Authored-By |
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# line(s) with a single "Co-Authored-By: <that value>" (appended if the |
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# commit had none). |
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# |
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# Identity arguments are in the usual git form: Name Surname <email@host> |
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# Commit dates are left untouched. |
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# |
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# WARNING: this rewrites history (commit SHAs change). filter-branch keeps a |
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# backup at refs/original/... ; undo with: |
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# git reset --hard refs/original/refs/heads/<branch> |
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# |
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set -euo pipefail |
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if [ "$#" -lt 1 ] || [ "$#" -gt 3 ]; then |
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echo "usage: $(basename "$0") <back_until_sha_inclusive> <committer_name_email> <coauthored_by_name_email>" >&2 |
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echo " (args 2 and 3 optional; omit arg 3 to strip Co-Authored-By lines," >&2 |
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echo " omit arg 2 to also fall back to the current git config identity)" >&2 |
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exit 2 |
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fi |
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SINCE="$1" |
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IDENT="${2:-}" |
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COAUTHOR="${3:-}" |
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# --- validate ------------------------------------------------------------- |
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if ! git rev-parse --is-inside-work-tree >/dev/null 2>&1; then |
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echo "error: not inside a git work tree" >&2 |
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exit 1 |
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fi |
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if ! git rev-parse --verify --quiet "${SINCE}^{commit}" >/dev/null; then |
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echo "error: '$SINCE' is not a valid commit" >&2 |
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exit 1 |
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fi |
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# Resolve the target identity: an explicit "Name <email>" argument, or the |
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# current git config user.name/user.email when arg 2 is omitted. |
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if [ -n "$IDENT" ]; then |
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case "$IDENT" in |
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*"<"*">"*) : ;; |
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*) echo "error: committer identity must look like 'Name <email>', got '$IDENT'" >&2; exit 1 ;; |
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esac |
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RA_NAME="$(printf '%s' "$IDENT" | sed -E 's/[[:space:]]*<[^>]*>[[:space:]]*$//')" |
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RA_EMAIL="$(printf '%s' "$IDENT" | sed -E 's/^[^<]*<([^>]*)>.*$/\1/')" |
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else |
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RA_NAME="$(git config user.name || true)" |
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RA_EMAIL="$(git config user.email || true)" |
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if [ -z "$RA_NAME" ] || [ -z "$RA_EMAIL" ]; then |
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echo "error: no identity given and git config user.name/user.email is unset" >&2 |
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exit 1 |
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fi |
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fi |
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if [ -n "$COAUTHOR" ]; then |
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case "$COAUTHOR" in |
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*"<"*">"*) : ;; |
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*) echo "error: co-author must look like 'Name <email>', got '$COAUTHOR'" >&2; exit 1 ;; |
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esac |
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fi |
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# Range that includes SINCE itself. If SINCE is the root commit it has no |
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# parent, so fall back to the full history reachable from HEAD. |
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if git rev-parse --verify --quiet "${SINCE}^{commit}^" >/dev/null; then |
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RANGE="${SINCE}~1..HEAD" |
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else |
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RANGE="HEAD" |
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fi |
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# --- awk program that rewrites the commit message ------------------------- |
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# Removes existing Co-Authored-By lines, trims trailing blank lines, and (when |
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# ca is non-empty) appends a single Co-Authored-By trailer, keeping it inside |
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# the trailing trailer block when one already exists. |
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AWK_PROG="$(mktemp "${TMPDIR:-/tmp}/reauthor.XXXXXX")" |
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trap 'rm -f "$AWK_PROG"' EXIT |
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cat > "$AWK_PROG" <<'AWK' |
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{ buf[NR] = $0 } |
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END { |
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m = 0 |
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for (i = 1; i <= NR; i++) { |
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if (tolower(buf[i]) ~ /^co-authored-by:/) continue |
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out[++m] = buf[i] |
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} |
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while (m > 0 && out[m] ~ /^[ \t]*$/) m-- # trim trailing blanks |
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for (i = 1; i <= m; i++) print out[i] |
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if (ca != "") { |
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if (m > 0 && out[m] ~ /^[A-Za-z0-9-]+:[ \t]/) { # last line already a trailer |
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print "Co-Authored-By: " ca |
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} else { |
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if (m > 0) print "" # blank line before trailer |
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print "Co-Authored-By: " ca |
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} |
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} |
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} |
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AWK |
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# --- rewrite -------------------------------------------------------------- |
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export RA_NAME RA_EMAIL COAUTHOR |
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ENV_FILTER=' |
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export GIT_AUTHOR_NAME="$RA_NAME" |
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export GIT_AUTHOR_EMAIL="$RA_EMAIL" |
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export GIT_COMMITTER_NAME="$RA_NAME" |
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export GIT_COMMITTER_EMAIL="$RA_EMAIL" |
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' |
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MSG_FILTER="awk -v ca=\"\$COAUTHOR\" -f \"$AWK_PROG\"" |
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if [ -n "$COAUTHOR" ]; then |
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echo "Reauthoring $RANGE as '$RA_NAME <$RA_EMAIL>', co-author -> '$COAUTHOR'" |
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else |
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echo "Reauthoring $RANGE as '$RA_NAME <$RA_EMAIL>', stripping Co-Authored-By lines" |
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fi |
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FILTER_BRANCH_SQUELCH_WARNING=1 git filter-branch -f \ |
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--env-filter "$ENV_FILTER" \ |
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--msg-filter "$MSG_FILTER" \ |
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-- $RANGE |
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echo |
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echo "Done. Backup ref kept at refs/original/. Undo with:" |
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echo " git reset --hard refs/original/refs/heads/$(git rev-parse --abbrev-ref HEAD)" |