Git Hooks

Git hooks are shell scripts that run automatically before or after Git executes an important command like Commit or Push.  They can be used to enforce conventions around git actions, such as branch names and commit messages.

Git hooks reside in .git/hooks. To enable a hook, just remove the .sample extension

Git Hook	Git Command	Description
applypatch-msg.sample	git am	When a patch message is changed
commit-msg.sample	git commit	To set the message of a commit action
fsmonitor-watchman.sample	launch watchman	To integrate watchman
post-update.sample	git push	By updating all data after the push
pre-applypatch.sample	git am	Before applying a patch
pre-commit.sample	git commit	Before committing
prepare-commit-msg.sample	git commit	When a commit message is set
pre-push.sample	git push	Before making a push
pre-rebase.sample	git rebase	Before making a pass or merge
pre-receive.sample	git push	When we push and get the data from the remote repository
update.sample	git push	By updating the remote data in a push

Reference: https://www.hostinger.com/tutorials/how-to-use-git-hooks/

While the directory .git/hooks is not version controlled, you can update your git hooks location to a versioned directory, such as .githooks

> git config core.hooksPath ./.githooks

Note: IntelliJIDE does not support custom hook locations, nor prepare-commit-msg

But you can use the plugin Git Commit Message Template w/ a matching regex such as #?[0-9]{6,10}


Branch Names
Having a common naming convention for branches can make it easier to determine what a branch is being used for.

Something like
ticket#-ShortDesc

123123-AddAuditLog
is more useful than 

addmorestuff
as you can at least track back the branch back to the originating ticket

The git hook pre-commit can be used to enforce branch names

File pre-commit:
#!/usr/bin/env bash

local_branch="$(git rev-parse --abbrev-ref HEAD)"

#valid_branch_regex="^(feature|bugfix|improvement|library|prerelease|release|hotfix)\/[a-z0-9._-]+$"
valid_branch_regex="^#?[0-9]{6,10}-[a-zA-Z]+$"

error()
{
  echo "GIT PRE-COMMIT HOOK ERROR:"
  echo "$1"
  echo ""
  echo "Your commit will be rejected."
  echo "You should rename your branch to a valid name and try again."
  exit 1
}

if [[ ! $local_branch =~ $valid_branch_regex ]]
then
  error "Branch names must match: $valid_branch_regex."
fi

exit 0

gist

Commit Messages
As git tends to intermingle commits from different branches based on time, you can also enforce comments to contain ticket numbers too.  

Something like
ticket# added audit log

as you can at least track back the commit back to the originating ticket
In general, you should try to make multiple commits grouped by concept, and commit every day or two.

The git hooks prepare-commit-msg and commit-msg
can be used to enforce ticket numbers in commits

File prepare-commit-msg:
#!/usr/bin/env bash

# commit message file
commit_msg_file="$1"
# condition the commit is invoked; none (git commit), message (git commit -m <msg>), template, merge, squash, or commit
# commit_source=$2
# commit hash
# sha1=$3

local_branch="$(git rev-parse --abbrev-ref HEAD)"
get_ticket_nbr="^#?([0-9]{6,10}).*"
valid_ticket_nbr="^[0-9]{6,10}$"

error() 

{
  echo "GIT PREPARE-COMMIT HOOK ERROR:"
  echo "$1"
  echo ""

  exit 1
}

# check if commit message already has the ticket # prepended
# if not, try to prepend
commit_msg=$(cat "$commit_msg_file")
if [[ ! $commit_msg =~ $get_ticket_nbr ]]
then
  if [[ $local_branch =~ $get_ticket_nbr ]]
  then
    ticket="${BASH_REMATCH[1]}"
    if [[ $ticket =~ $valid_ticket_nbr ]]
    then
      echo "#${ticket} " > "$commit_msg_file"
      echo "$commit_msg" >> "$commit_msg_file"
    fi
  fi
fi

exit 0

gist 

File commit-msg:
#!/usr/bin/env bash

# commit message file
commit_msg_file="$1"

valid_comment_prefix="^#?[0-9]{6,10} .+"

error() 

{
cp "$commit_msg_file" "_gitmsg.saved.txt"

echo "GIT COMMIT-MSG HOOK ERROR:"
echo "$1"
echo ""
echo "Original checkin message has been stored in '_gitmsg.saved.txt'"
echo "Your commit will be rejected."
echo "You should update your commit and try again."

exit 1
}

commit_msg=$(cat "$commit_msg_file")
if [[ ! $commit_msg =~ $valid_comment_prefix ]]
then
  error "Comment must match: $valid_comment_prefix"
fi

exit 0

gist


Note: hooks can be tested using 

> bash .githooks\prepare-commit-msg test.txt


You should now have some ideas on how to enforce some consistency in your git actions.

-End of Document-

Thanks for reading