nocheckin pre-commit hook for Git

pre-commit-nocheckin

#!/bin/bash
# Author: xezrunner (github.com/xezrunner)
# Inspired by Jonathan Blow's nocheckin setup with SVN (twitch.tv/j_blow) (youtube.com/@jblow888)
# Credits to DustinGadal on r/Jai: reddit.com/r/Jai/comments/jp0vjy/nocheckin_behavior_in_gitsourcetree/gbfhzd1

# gist.github.com/xezrunner/e6dbafcc21fcbc976c93bdee0f371a08

# This pre-commit hook checks for the keyword "$NOCHECKIN_KEYWORD" in staged files,then aborts the commit
# if any matches were found, with output of file path, line number and match preview.

# Required programs/utilities: git, grep, xargs, wc (optional: awk for nicer formatting)

# To install, copy and rename to <repo>/.git/hooks/pre-commit (merge contents if already exists)
# The file name has to be "pre-commit" for Git to use it. It is also compatible with git GUIs.
# On Unix, mark the file as executable with `chmod +x .git/hooks/pre-commit`.

DEFAULT_KEYWORD='nocheckin'

# Settings (can override from environment):
NOCHECKIN_KEYWORD=${NOCHECKIN_KEYWORD:-$DEFAULT_KEYWORD}
NOCHECKIN_ENABLE_AWK_FORMATTING=${NOCHECKIN_ENABLE_AWK_FORMATTING:-1} # only if SUPPORTS_AWK_FORMATTING=1 (system has awk)
NOCHECKIN_MAX_COLUMNS=${NOCHECKIN_MAX_COLUMNS:-120}

# Define colors only when in a console and it supports them (GUIs like Github Desktop wouldn't parse these at all):
ncolors=$(tput colors)
if test -t 1 && test -n "$ncolors" && test $ncolors -ge 8; then
    HAS_COLORS=1
	CL_RED=$'\033[31m'
	CL_BOLDRED=$'\033[1;31m'
	CL_NONE=$'\033[0m'
fi

OUTPUT_MESSAGE="${CL_BOLDRED}Error:${CL_NONE} '$NOCHECKIN_KEYWORD' found in staged files:"

# Get staged files containing the search target
# --staged: only look at files that have been added to staging (pre-commit)
# --diff-filter=d: exclude files that contain the keyword, but are staged for deletion
SEARCH_CMD="git diff --staged --diff-filter=d --name-only --relative -i -G $NOCHECKIN_KEYWORD"

# Scanning:
GREP_CMD="grep -H $NOCHECKIN_KEYWORD -i -n --color=auto" # <filename>:line******

SUPPORTS_AWK_FORMATTING=$(command -v awk >/dev/null 2>&1 && [ "$HAS_COLORS" = "1" ] && echo 1)
GREP_CMD_AWK="grep --color=never -n -i -C 1 "$NOCHECKIN_KEYWORD""

process_file() {
    if [ "$NOCHECKIN_ENABLE_AWK_FORMATTING" != "1" ] || [ "$SUPPORTS_AWK_FORMATTING" != 1 ]; then
		$GREP_CMD "$file"; return
    fi

    echo "  - in $1:" # in <file>:
    $GREP_CMD_AWK "$file" | \
    
    # Replace - or : for line numbers with a known delimiter:
    sed -E 's/^([0-9]+)[:|-]/\1<nocheckin_grep_delimiter>/' | \

    # Format output: '<line>: ...<match>...', newline between match groups
	awk -v keyword="$NOCHECKIN_KEYWORD" -v maxlen=$NOCHECKIN_MAX_COLUMNS '
	{
        if ($0 == "--") { print ""; next } # newline on match groups

        split($0, parts, /<nocheckin_grep_delimiter>/)
		line_num = parts[1]
		content  = parts[2]

		if (length(content) == 0) next # skip empty lines
        
		keyword_pos = index(tolower(content), tolower(keyword)) # find keyword position
		if (!keyword_pos) keyword_pos = 1
		start = 1; end = length(content)

        # Truncate lines:
		if (length(content) > maxlen) {
			if (keyword_pos > maxlen/2)   start = keyword_pos - int(maxlen/2) # adjust start to center keyword
			if (start + maxlen - 1 < end) end   = start + maxlen - 1          # clamp end to limit if it does not fit
			else                          start = end - maxlen + 1            # otherwise, move start point
            
			if (start < 1) start = 1 # clamp
		}
        
		preview = substr(content, start, end-start+1)      # assemble
		if (start > 1)             preview = "..." preview # add truncation marks
		if (end < length(content)) preview = preview "..."

        print line_num": " preview
	}
    ' | \
    grep --color=auto -i -E 'nocheckin|$' # highlight matches
}

# Main:
files=($($SEARCH_CMD))
if (( ${#files[@]} > 0 )); then
	echo -e $OUTPUT_MESSAGE

	for ((i=0; i<${#files[@]}; i++)); do
		file="${files[$i]}"
        process_file "$file"

		if [ $i -lt $((${#files[@]}-1)) ]; then echo; fi # newline between files
	done

	exit 1 # abort commit
fi

pre-commit-nocheckin.md

nocheckin pre-commit hook for Git

This Git pre-commit hook checks for a keyword ("nocheckin" by default) in staged source files and aborts the commit if any matches are found, with the output of file path, line number and match preview.

This is inspired by Jonathan Blow's nocheckin setup with SVN, as seen on his programming sessions at Twitch and YouTube.
Additional credit to DustinGadal on the r/Jai subreddit for original implementation.

Tested on Linux (GNOME OS 49 aarch64) and macOS arm64.

Installation

As a download:

1. Download the file from above, either by clicking Download ZIP and extracting it, or by clicking Raw and saving the contents to a file.
2. Copy the pre-commit-nocheckin (or saved) file and rename it to <repo>/.git/hooks/pre-commit. If you already have a pre-commit hook, merge it into the file.
3. On Unix systems, you will likely need to mark the file as executable by running chmod +x ./git/hooks/pre-commit. Git will warn about this when issuing a commit if it's the case, though it will perform that commit without running this hook.

⚠️ NOTE: The file name has to be "pre-commit" for Git to recognize and use it as a pre-commit hook.

Manually:

1. Copy the contents of the file from above.
2. Create <repo>/.git/hooks/pre-commit and paste the contents, or merge if exists.

Usage

CLI:

1. Stage files with git add <file> ...
2. Attempt making a commit with git commit ...
3. Observe the commit failing when at least one of the staged files contains a nocheckin.

GUI (Github Desktop)

1. Mark files for staging.
2. Attempt making a commit.
3. Observe the commit failing when at least one of the staged files contains a nocheckin.

Changing the keyword

You can change the keyword that's used for rejecting commits by setting the NOCHECKIN_KEYWORD variable through the environment, or editing the default at the top of the script (DEFAULT_KEYWORD)

Any case-insensitive occurance of the keyword will reject a commit, whether it is part of a comment or is used within the code.

Environment variables

• NOCHECKIN_KEYWORD: The keyword used for rejecting commits.
  Default: nocheckin
• NOCHECKIN_ENABLE_AWK_FORMATTING: Whether to use nicer output formatting when available.
  Default: 1
• NOCHECKIN_MAX_COLUMNS: How many columns to aim for when using nicer output formatting.
  Default: 120

Screenshots

Command-line example:

GitHub Desktop GUI example: