Git hook to reject commits where files contain a specific string

Question

I am using Guard with Rspec; I use focus: true to force it run only tests I am working on. But sometimes I forget to remove focu

Answer 1

Building off the existing answers, here is the version I am using with support for multiple strings.

#!/bin/sh

declare -a arr=("This is the first string." "This is the second string.")

for i in "${arr[@]}"
do
    git diff --cached --name-only | xargs grep --with-filename -n $i && echo "COMMIT REJECTED! Found '$i' references. Please remove them before commiting." && exit 1
done

exit 0

Answer 2

Server-Side Git Hooks

I came up with this example for the use case of code formatting, but pretty much if you just replace the usage of Prettier with grep -r 'bad-thing' it should work as well:

ref_name=$1
new_rev=$3

# only check branches, not tags or bare commits
if [ -z $(echo $ref_name | grep "refs/heads/") ]; then
  exit 0
fi

# don't check empty branches
if [ "$(expr "${new_rev}" : '0*$')" -ne 0 ]; then
  exit 0
fi

# Checkout a copy of the branch (but also changes HEAD)
my_work_tree=$(mktemp -d -t git-work-tree.XXXXXXXX) 2>/dev/null
git --work-tree="${my_work_tree}" --git-dir="." checkout $new_rev -f >/dev/null

# Do the formatter check
echo "Checking code formatting..."
pushd ${my_work_tree} >/dev/null
prettier './**/*.{js,css,html,json,md}' --list-different
my_status=$?
popd >/dev/null

# reset HEAD to master, and cleanup
git --work-tree="${my_work_tree}" --git-dir="." checkout master -f >/dev/null
rm -rf "${my_work_tree}"

# handle error, if any
if [ "0" != "$my_status" ]; then
  echo "Please format the files listed above and re-commit."
  echo "(and don't forget your .prettierrc, if you have one)"
  exit 1
fi

There are some limitations to this, so I'd recommend taking a look at the "more complete" version as well:

• Reject Ugly Commits with Server-Side Git Hooks

The Gist of it...

If you want to do this server-side you'll be working with a bare repository (most likely), so you have to do a little bit of extra work to create a temporary place to check things out (as shown above).

Basically, this is the process:

• use a server-side update hook (similar to pre-receive)
• inspect the branch and commit
• checkout the bare repo to a temp folder
• run the check for specific string (grep -r 'bad-thing' .)
• exit non-zero if there are offending files

And I would have adjusted the script to do the greping, but it's late (or rather very early) and I don't trust myself to not make a typo that breaks everything in trying to make a "simple" change. I know that the above works (because I've used it), so I'll leave at that.

HTH (not the OP per se, but others in the future - and perhaps myself again)

Answer 3

A good source of information is the book at git-scm.

You want the pre-commit hook. To return a non-zero value (and thus abort the commit), you'd want something along these lines:

FILES_PATTERN='\.rb(\..+)?$'
FORBIDDEN='focus: true'
git diff --cached --name-only | \
  grep -spec/ | \
  grep -E $FILES_PATTERN | \
  xargs grep --with-filename -n $FORBIDDEN && echo "COMMIT REJECTED Found '$FORBIDDEN' references. Please remove them before commiting" && exit 1

That's lifted from this rather good tips site. I haven't tested the tweaks I made.