Can a Git hook automatically add files to the comm

Question

I'd like to add an automatically generated file to the same commit using a pre- or post-commit hook in Git, dependent on the files that were modified in that commit. How would I go about this?

I've tried this as a pre-commit hook, but no luck:

#!/bin/sh
files=`git diff --cached --name-status`
re="<files of importance>"
if [[ $files =~ $re ]]
then
  echo "Creating files"
  exec bundle exec create_my_files
  exec git add my_files
  exec git commit --amend -C HEAD
fi

This successfully adds them to the repository, but does not add them to the commit. I've also tried using the last two exec lines in a post-commit hook along with the pre-commit inspection, but no good either.

Answer 1

You could use a combination of a pre and post commit script.

In the pre-commit:

• Touch a file .commit or something. (be sure to add this to .gitignore)

In the post-commit:

if .commit exists you know a commit has just taken place but a post-commit hasn't run yet. So, you can do your code generation here. Additionally, test for .commit and if it exists:

• add the files
• commit --ammend -C HEAD --no-verify (avoid looping)
• delete .commit file

This is roughly the process I use to store a .metadata file in the repository generated from metastore.

If anyone knows a better way I'm all ears but it seems to work for now.

Answer 2

You can use update-index:

git update-index --add my_files

Answer 3

I had the same need and this approach worked pretty well for me:

#!/bin/sh
files='git diff --cached --name-only'
re="<files of importance>"
if [[ $files =~ $re ]]
then
   echo "Creating files"
   create_my_files && git add my_files
fi

where "create_my_files" should be executable, for example if it is a python file you could execute it as "python create_my_files && git add my_files"

and is true you don't need a pre-commit to commit again (that would create a infinite nasty loop :p)

Answer 4

Yes, you can add generated files automatically on the commit using git hooks! But it requires a tricky script.

Here you can find the problem solved. There, it is updating the file version on every commit, adding a new modified file and amending the commit as you need it to. It is fully working: https://github.com/evandrocoan/.versioning

Then you just replace the 'Version File Replacement' algorithm on the file 'updateVersion.sh', by your algorithm. Maybe you need to change a few things like, remove the branch limitation, because there, the script only runs if you are on the 'develop' branch.

Also, it will only change the specified file, if is staged. If the file is not staged, then it will do nothing than the normal/usual commit. More precisely, it print out what it is doing on every step.

I am going to explain, that trick. It is quite tricky. On the prepare-commit-msg-hook, it detects whether the desired file is being staged and committed. After that, it creates a flag file, and stops the prepare-commit-msg-hook. Later on the post-commit-hook, it checks whether the flag file exists. If yes, it amends the files on the commit.

Attention, it would create a infinity loop because it would call again the prepare-commit-msg-hook (as we are amending). But it does not happen because of the flag file. When the prepare-commit-msg-hook runs and find the flag file, it "knows" what is happening. Then is just deletes the flag file and do not create it again. Doing it, it will block the post-commit-hook from amending again the commits, allowing the commit to finish for good.