Question

I’m currently thinking of changing my VCS (from subversion) to git. Is it possible to limit the file size within a commit in a git repository? For e. g. subversion there is a hook: http://www.davidgrant.ca/limit_size_of_subversion_commits_with_this_hook

From my experience people, especially those who are inexperienced, sometimes tend to commit files which should not go into a VCS (e. g. big file system images).

Answer 1

As I was struggling with it for a while, even with the description, and I think this is relevant for others too, I thought I’d post an implementation of how what J16 SDiZ described could be implemented.

So, my take on the server-side update hook preventing too big files to be pushed:

#!/bin/bash

# Script to limit the size of a push to git repository.
# Git repo has issues with big pushes, and we shouldn't have a real need for those
#
# eis/02.02.2012

# --- Safety check, should not be run from command line
if [ -z "$GIT_DIR" ]; then
        echo "Don't run this script from the command line." >&2
        echo " (if you want, you could supply GIT_DIR then run" >&2
        echo "  $0 <ref> <oldrev> <newrev>)" >&2
        exit 1
fi

# Test that tab replacement works, issue in some Solaris envs at least
testvariable=`echo -e "\t" | sed 's/\s//'`
if [ "$testvariable" != "" ]; then
        echo "Environment check failed - please contact git hosting." >&2
        exit 1
fi


# File size limit is meant to be configured through 'hooks.filesizelimit' setting
filesizelimit=$(git config hooks.filesizelimit)

# If we haven't configured a file size limit, use default value of about 100M
if [ -z "$filesizelimit" ]; then
        filesizelimit=100000000
fi

# Reference to incoming checkin can be found at $3
refname=$3

# With this command, we can find information about the file coming in that has biggest size
# We also normalize the line for excess whitespace
biggest_checkin_normalized=$(git ls-tree --full-tree -r -l $refname | sort -k 4 -n -r | head -1 | sed 's/^ *//;s/ *$//;s/\s\{1,\}/ /g' )

# Based on that, we can find what we are interested about
filesize=`echo $biggest_checkin_normalized | cut -d ' ' -f4,4`

# Actual comparison
# To cancel a push, we exit with status code 1
# It is also a good idea to print out some info about the cause of rejection
if [ $filesize -gt $filesizelimit ]; then

        # To be more user-friendly, we also look up the name of the offending file
        filename=`echo $biggest_checkin_normalized | cut -d ' ' -f5,5`

        echo "Error: Too large push attempted." >&2
        echo  >&2
        echo "File size limit is $filesizelimit, and you tried to push file named $filename of size $filesize." >&2
        echo "Contact configuration team if you really need to do this." >&2
        exit 1
fi

exit 0

Note that it’s been commented that this code only checks the latest commit, so this code would need to be tweaked to iterate commits between $2 and $3 and do the check to all of them.