Git pre-commit - Another check to ensure clean code

5 minutes • 2011-11-13 | git how-to 

Throughout my career I have been using various revision control systems. I started off with Visual SourceSafe which I thought at the time was great, primarily because of the small size of our team and the ease of use though the Visual Basic’s IDE.

Later on I switched to SVN which is a great version control system, and it fulfilled all my needs for proper version control.

When I moved to the US and started working here, I introduced SVN to the company that I was working at the time. We adopted the technique of having one branch per project, since we were working on different projects at any given time. Using the plugin through Eclipse or in Windows the integrated Explorer plugin, I was checking in code, switching through projects etc.

Recently I changed jobs, and although we did use Subversion for a few months, we did switch to Git. The reasons behind it are too many to count - and I will probably go through them in another blog post.

One really good feature that Git has is its hooks. Although Subversion also supports hooks, I have only been exposed to the ones from Git and have used them - hence this blog post.

Git comes with some predefined hooks that one can use as a starting point. The code is checked before it is being committed and if it does pass whatever the pre-commit (for instance) hook does, it will allow you to commit; alternatively it will stop until you correct the mistakes made.

One very popular pre-commit hook is the one here by Remigijus Jarmalavičius. It checkes the files that have been modified/added and runs the php -l on it to ensure that whatever will be committed does not have PHP syntax errors.

I have downloaded that code and easily added it to my repository so everything is being checked prior to any of my commits.

In our MemberFuse™ platform, we have - like any other developer - many helper functions that are used solely for development. One of the mostly used one is the vdd($message);. What this function does is a var_dump of the $message variable, echoes out the file that it was called as well as the line it is in, and dies. It is great for quick and dirty debugging and inspecting a variable as it passes through the code. Granted it is not very TDD but I am sure that all developers have little things like these to aid them with their daily programming and debugging.

From time to time, as we fix bugs and explore certain behaviors that sometimes it is difficult to assess, we use this function and we output the data on the browser. However this is just a development/debugging function and must never be used (or enabled) in the production environment.

I have been the culprit of using the function, forgot that I had it in a certain part of the code, and committed that code in our development branch. That caused some colleagues to experience inconsistent behavior with errors showing up on the screen and time was wasted.

To combat this scenario, I wrote a pre-commit hook that will allow you to check for the existence of certain functions in the code and ensure that those functions (or strings for that matter since I am using [grep]) do not exist in what is to be committed.

The pre-commit hook that I wrote is listed below and the code has been heavily based on Remigijus Jarmalavičius’s pre-commit syntax checker.

# Author: Nikolaos Dimopoulos <nikos"">
# Based on code by Remigijus Jarmalavičius <remigijus""> 
# Checks the files to be committed for the presence of print_r(), 
# var_dump(), die()
# The array below can be extended for further checks


let "element_count = $element_count + 1"

LIST=$(git status | grep -e '\#.*\(modified\|added\)')
for file in $LIST
    if [ "$file" == '#' ]; then
    if [ $(echo "$file" | grep 'modified') ]; then
    elif [ $(echo "$file" | grep 'added') ]; then
        EXTENSION=$(echo "$file" | grep ".php$")
        if [ "$EXTENSION" != "" ]; then

            while [ "$index" -lt "$element_count" ]
                echo "Checking $FILE_ACTION file: $file [${checks[$index]}]" 
                ERRORS=$(grep "${checks[$index]}" $ROOT_DIR$file &gt;&amp;1)
                if [ "$ERRORS" != "" ]; then
                    if [ "$ERRORS_BUFFER" != "" ]; then
                    echo "${checks[$index]} found in file: $file "
                let "index = $index + 1"
if [ "$ERRORS_BUFFER" != "" ]; then
    echo "These errors were found in try-to-commit files: "
    echo -e $ERRORS_BUFFER
    echo "Can't commit, fix errors first."
    exit 1
    echo "Commited successfully."

If you want to check for any kind of string, just add one extra line (or modify the existing ones) of the checks array. The code will loop through the array and grep the modified/added files for that entry. If it is found the commit will not be allowed and you will have to manually go and change whatever needs to be changed.

I hope you find this hook useful. You can download the file from my github repository.

Note: If you wish to run more than one pre-commit hooks, you don’t need to merge them all in the same file. You can create a pre-commit file which will have the following contents:


DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"


The *.l file is the one that runs the PHP syntax check, while the *.output one is the one mentioned in this blog post. You can extend the list to your liking and usage.


  • Nikolaos Dimopoulos

    Boldly goes where no other coder has gone before.... and other ramblings

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