exit 1 in pre-commit doesn't abort git commit?

Question

I'm aborting git commit if a certain condition is met.

check if my commit has 'import pdb' in emacs/git?

#!/bin/sh

git diff --cached --no-renames --name-status --diff-filter=AM |
  while read st file; do
    case "$file" in
    *.py)
        if git show ":$file" |
          grep -E "^[^#]*\bimport[[:space:]]+pdb\b"; then
            echo "$file: has import pdb"
            exit 1
        fi;;
    esac
done

git diff --cached --name-status --diff-filter=ACM | while read st file; do
    if grep "#[[:space:]]*@test" "$file"; then
        echo "$file: has @test"
        exit 1
    fi
done

The code runs fine and I can see the log "... has import pdb" But the next line exit 1 won't abort the git commit.

It used to work fine, but it stopped working at some point. I'm on git 1.9.1

---

output

$ GIT_TRACE=2 git commit
trace: built-in: git 'commit'
trace: run_command: '.git/hooks/pre-commit'
trace: built-in: git 'diff' '--cached' '--no-renames' '--name-status' '--diff-filter=AM'
trace: built-in: git 'show' ':momsite/apps/custom_push_notifications/utils.py'
    import pdb; pdb.set_trace()
momsite/apps/custom_push_notifications/utils.py: has import pdb
trace: built-in: git 'diff' '--cached' '--name-status' '--diff-filter=ACM'
trace: run_command: 'emacs' '/home/eugenekim/Documents/zibann/.git/COMMIT_EDITMSG'
trace: exec: 'emacs' '/home/eugenekim/Documents/zibann/.git/COMMIT_EDITMSG'

Answer 1

The first part of the code reads like

something | while ...; do ... exit 1; done

Since a pipe necessarily involves two processes, the shell has to fork a subshell to execute your while loop. As a result, exit 1 exists from the subshell with status 1, and returns to your parent shell, which ignores the return code.

You want to add a || exit $? after the done keyword, like this:

something | while ...; do ... exit 1; done || exit $?

Note that this is not actually a Git question, but a shell issue.