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git pre-commit hook preventing large files

Usage

You can use in two ways.

  1. Directly as the pre-commit hook in your .git/hooks folder.

  2. With Husky by updating your package.json with:

"husky": {
    "hooks": {
      "pre-commit": "sh ./some-path/pre-commit-prevent-large-files.sh"
    }
}

Installation

@guysmoilov wrote an awesome installer script over here that means this hook will be added to all future repos you clone; how cool!

Credits

Based on @kiwidamien's original gist here

Alternatives

pre-commit is "a framework for managing and maintaining multi-language pre-commit hooks" and has a hook you can plug-in called: check-added-large-files. pre-commit is built with Python though, so you'll need Python installed.

#!/bin/bash
# This is a pre-commit hook that ensures attempts to commit files that are
# larger than $limit to your _local_ repo fail, with a helpful error message.
# Maximum file size limit in bytes
limit=$(( 5 * 2**20 )) # 5MB
limitInMB=$(( $limit / 2**20 ))
# Move to the repo root so git files paths make sense
repo_root=$( git rev-parse --show-toplevel )
cd $repo_root
empty_tree=$( git hash-object -t tree /dev/null )
if git rev-parse --verify HEAD > /dev/null 2>&1
then
against=HEAD
else
against="$empty_tree"
fi
# Set split so that for loop below can handle spaces in file names by splitting on line breaks
IFS='
'
echo "Checking staged file sizes"
shouldFail=false
# `--diff-filter=d` -> skip deletions
for file in $( git diff-index --cached --diff-filter=d --name-only "$against" ); do
# Skip for directories (git submodules)
if [[ -f "$file" ]]; then
file_size=$( ls -lan $file | awk '{ print $5 }' )
if [ "$file_size" -gt "$limit" ]; then
echo File $file is $(( $file_size / 2**20 )) MB, which is larger than our configured limit of $limitInMB MB
shouldFail=true
fi
fi
done
if $shouldFail
then
echo If you really need to commit this file, you can push with the --no-verify switch, but the file should definitely, definitely be under $limitInMB MB!!!
echo Commit aborted
exit 1;
fi
@benmccallum
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benmccallum commented Jan 26, 2021

cc: @guysmoilov, you might want to make these updates to your gist too

@Cyberbeni
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Cyberbeni commented Jan 26, 2021

I've updated the gist with all your feedback everything except one I'm not sure about (see below). Do you mind checking it looks OK now to you?

Also I think it would be better to use /bin/bash shebang: https://askubuntu.com/a/141932

Do you mean in the example usage? e.g. it should be this?
"pre-commit": "!/bin/sh ./some-path/pre-commit-prevent-large-files.sh"

No, I mean the first line in the file should be #!/bin/bash instead of #!/bin/sh because the latter can be different based on OS

@benmccallum
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benmccallum commented Feb 1, 2021

Thanks @Cyberbeni, updated

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