Merge pull request #543 from lotuszhaol/feat/blame-horizon

Add blame horizon utility

Author: fridayjoshi

blame-horizon/README.md

@@ -0,0 +1,29 @@
+# Blame Horizon
+
+A tiny Bash script that filters `git blame` by time for one file. By default, it prints lines last changed on or after `--since`; with `--older`, it prints lines changed before the cutoff.
+
+## Usage
+
+Run from the repository root:
+
+```bash
+bash blame-horizon/blame_horizon.sh --since 2025-01-01 -f README.md
+bash blame-horizon/blame_horizon.sh --since "1 week ago" --older --file README.md
+bash blame-horizon/blame_horizon.sh --since 2025-01-01 --csv -f README.md > recent.csv
+```
+
+Run `bash blame-horizon/blame_horizon.sh --help` for more details.
+
+## Sample Output
+
+```text
+80847477 (2026-02-14, Harsh Joshi)      3  ### Note - 100LinesOfCode is now actively maintained by my AI Friday - github.com/fridayjoshi
+```
+
+```text
+sha,date,author,line_no,line_text
+80847477,2026-02-14,"Harsh Joshi",3,"### Note - 100LinesOfCode is now actively maintained by my AI Friday - github.com/fridayjoshi"
+c1235362,2026-02-14,"Harsh Joshi",4,""
+```
+
+Requires Bash 4+, Git, and GNU `date`.

blame-horizon/blame_horizon.sh

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+#!/usr/bin/env bash
+# Filter `git blame` by cutoff time; --older flips the comparison.
+# Requires: bash 4+, git, GNU date (coreutils).
+set -euo pipefail
+
+PROG=${0##*/}
+DATE_BIN=${DATE_BIN:-date}
+
+BH_TMPFILE=""
+trap '[[ -n $BH_TMPFILE ]] && rm -f -- "$BH_TMPFILE"' EXIT
+
+die() { printf 'error: %s\n' "$*" >&2; exit 1; }
+
+usage() {
+	cat >&2 <<EOF
+Usage: $PROG --since <date|datetime> --file <path> [--older] [--csv]
+       $PROG -h | --help
+
+Options:
+  --since <when>   Required. YYYY-MM-DD (UTC midnight) or any GNU date string.
+  --file, -f <p>   Required. Path passed to \`git blame\`.
+  --older          Show lines last changed BEFORE --since (default: on/after).
+  --csv            Emit CSV (header + RFC 4180 quoting) instead of text.
+  -h, --help       Show this help and exit.
+
+Requires: bash 4+, git, GNU date.
+EOF
+}
+
+# Bare YYYY-MM-DD is normalized to 00:00:00 UTC that day (same as README).
+since_epoch() {
+	local s=$1 out
+	[[ $s =~ ^[0-9]{4}-[0-9]{2}-[0-9]{2}$ ]] && s="$s 00:00:00"
+	out=$("$DATE_BIN" -u -d "$s" +%s 2>/dev/null) || true
+	[[ $out =~ ^[0-9]+$ ]] || die "invalid --since: not a valid GNU date string: $1"
+	printf '%s\n' "$out"
+}
+
+# CSV doubles embedded quotes (RFC 4180).
+emit_row() {
+	local mode=$1 ts=$2 author=$3 line=$4 line_no=$5 sha=$6 day qa ql
+	day=$("$DATE_BIN" -u -d "@$ts" +%F)
+	if ((mode)); then
+		qa=${author//\"/\"\"}
+		ql=${line:1}; ql=${ql//\"/\"\"}
+		printf '%s,%s,"%s",%d,"%s"\n' "${sha:0:8}" "$day" "$qa" "$line_no" "$ql"
+	else
+		printf '%s (%s, %s) %6d  %s\n' "${sha:0:8}" "$day" "$author" "$line_no" "${line:1}"
+	fi
+}
+
+main() {
+	local since="" path="" older=0 csv=0 cutoff sha line_no author="" author_time="" committer_time="" ts n=0 line
+	while (($#)); do
+		case $1 in
+		--since)
+			(($# >= 2)) || { usage; die "--since requires a value"; }
+			since=$2
+			shift 2
+			;;
+		--file | -f)
+			(($# >= 2)) || { usage; die "--file requires a path"; }
+			path=$2
+			shift 2
+			;;
+		--older) older=1; shift ;;
+		--csv) csv=1; shift ;;
+		-h | --help) usage; exit 0 ;;
+		*) usage; die "unexpected argument: $1 (use --file/-f for the path)" ;;
+		esac
+	done
+	[[ -n $since ]] || { usage; die "--since is required"; }
+	[[ -n $path ]] || { usage; die "--file is required"; }
+
+	command -v git >/dev/null 2>&1 || die "git not found in PATH"
+	if ! "$DATE_BIN" --version >/dev/null 2>&1; then
+		if command -v gdate >/dev/null 2>&1 && gdate --version >/dev/null 2>&1; then
+			DATE_BIN=gdate
+		else
+			die "GNU date required; install coreutils or set DATE_BIN=/path/to/gdate"
+		fi
+	fi
+
+	cutoff=$(since_epoch "$since")
+
+	BH_TMPFILE=$(mktemp "${TMPDIR:-/tmp}/${PROG}.XXXXXX") || die "mktemp failed"
+	git blame --line-porcelain -- "$path" >"$BH_TMPFILE" || die "git blame failed"
+	((csv)) && echo 'sha,date,author,line_no,line_text'
+
+	# Porcelain records end with the TAB-prefixed source line.
+	while IFS= read -r line || [[ -n $line ]]; do
+		case $line in
+		author\ *) author=${line#author } ;;
+		author-time\ *) author_time=${line#author-time } ;;
+		committer-time\ *) committer_time=${line#committer-time } ;;
+		$'\t'*)
+			ts=${author_time:-${committer_time:-0}}
+			if (( (ts >= cutoff) ^ older )); then
+				emit_row "$csv" "$ts" "${author:-?}" "$line" "$line_no" "$sha"
+				((++n))
+			fi
+			;;
+		*)
+			# Header: SHA, source line no., final line no.
+			[[ $line =~ ^([0-9a-fA-F]{40}|[0-9a-fA-F]{64})[[:space:]]+[0-9]+[[:space:]]+([0-9]+) ]] && {
+				sha=${BASH_REMATCH[1],,}
+				line_no=${BASH_REMATCH[2]}
+				author="" author_time="" committer_time=""
+			}
+			;;
+		esac
+	done <"$BH_TMPFILE"
+
+	((n)) || echo "No matching lines." >&2
+}
+
+main "$@"