How to manage fugitive commit with a git pre-commit hook?

Question

When working on a git project in vim, I use the fugitive plugin.

I like to open a :Gstatus split, press - to add file and then press C to commit my changes. I also have a git pre-commit hook, it runs some test. In case of an error, it prompts me to make sure if I still want to commit.

But, when following this pattern, I don't see the output for the tests, neither the final prompt. Instead, vim freezes while the tests are running.

How would I make fugitive and a pre-commit hook get along together smoothly?

Update: This is the prompt in the git pre-commit hook:

#!/bin/bash
exec < /dev/tty

while true; do
  read -p "There were some errors in the test, do you still want to commit? (Y/n) " yn
  if [ "$yn" = "" ]; then
    yn='Y'
  fi
  case $yn in
      [Yy] ) break;;
      [Nn] ) exit;;
      * ) echo "Answer y or n.";;
  esac
done

Answer 1

On line 1019 of plugin/fugive.vim we can see how the :Gcommit command executes git:

noautocmd silent execute '!'.command.' > '.outfile.' 2> '.errorfile

With the variables replaced, the command looks like:

!env GIT_EDITOR=false git --git-dir=/home/martin/git-test/.git commit  > /tmp/vC4Lbak/1 2> /tmp/vC4Lbak/2

Notice the env GIT_EDITOR=false, this is just to prepare the .git/COMMIT_EDITMSG and checking if any error occurred! We then open a new buffer with COMMIT_EDITMSG which the user can edit, and after this is saved, we run git commit again.

Fugitive also uses stderr for error checking, and the pre-commit hook outputs to stderr (not stdout!)

You could work around this by extensively modifying this function, but I would say that running interactive pre-commit hooks is incompatible with how :Gcommit works, the hook would be run twice, and you lose error detection.

So you'll have to run git commit from outside of Vim, or use !git commit from Vim which will work fine, except that it will launch a second Vim instance for the commit message (unless you use -m).

You can create a command for this like so:

:command! Commit !git commit