First week - Pre-commit hooks

I wanted to study gits hook system, and decided to write a local pre-commit hook that tests the commited file size, as the course requirements state that there should not be any large files in the git repository. I decided to set the file size limit to 3 megabytes, as that seemed big enough for anything that is needed in the course.

I can get the list of commited files with command (according to this link)

git diff --cached --name-only --diff-filter=ACM

The weird `–diff-filter=ACM`` is defined in man git-diff as

Added (A), Copied (C), Deleted (D), Modified (M), Renamed (R), have their type (i.e. regular file, symlink, submodule, …​) changed (T), are Unmerged (U), are Unknown (X), or have had their pairing Broken (B).

To check file size in bash: https://stackoverflow.com/questions/5920333/how-can-i-check-the-size-of-a-file-using-bash

file=file.txt
minimumsize=90000
actualsize=$(wc -c <"$file")
if [ $actualsize -ge $minimumsize ]; then
    echo size is over $minimumsize bytes
else
    echo size is under $minimumsize bytes
fi

Go to .git/hooks/ folder in your repository. Add a pre-commit file to that directory (with touch pre-commit). Added the following script to the file to test its functionality:

#!/bin/sh

for file in $(git diff --cached --name-only --diff-filter=ACM);
do
  minimumsize=3000000
  actualsize=$(wc -c <"$file")
  echo $file
  if [ $actualsize -ge $minimumsize ]; then
    echo size is over $minimumsize bytes
  else
    echo size is under $minimumsize bytes
  fi

done

The file needed to be executable, so I called chmod +x pre-commit to change its executing permissions.

This was tested with a long list of unnecessary commits to the local repository.

In the end, I updated the file to its final form:

#!/bin/sh

for file in $(git diff --cached --name-only --diff-filter=ACM);
do
  maxsize=500000
  actualsize=$(wc -c <"$file")
  if [ $actualsize -ge $maxsize ]; then
    echo $file is over $maxsize bytes
    exit 1
  fi

done