docs(prepare-commit-msg): add additional information to tutorial

Author: crai0

docs/tutorials/auto_prepare_commit_message.md

@@ -2,7 +2,20 @@
 
 ## About
 
-To automatically prepare a commit message prior to committing, you can use a [Git hook](https://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks).
+It can be desirable to use commitizen for all types of commits (i.e. regular, merge,
+squash) so that the complete git history adheres to the commit message convention
+without ever having to call `cz commit` manually.
+
+To automatically prepare a commit message prior to committing, you can
+use a [Git hook](prepare-commit-msg-docs):
+
+> The [prepare-commit-msg] hook is invoked by git-commit right after preparing the
+> default log message, and before the editor is started.
+
+This allows for enforcing the usage of commitizen so that whenever a commit is about to
+be created, commitizen is used for creating the commit message. Running `git commit` or
+`git commit -m "..."` for example, would trigger commitizen and use the generated commit
+message for the commit.
 
 ## How to
 
@@ -25,3 +38,8 @@ exec < /dev/tty && cz commit --dry-run --write-message-to-file $COMMIT_MSG_FILE
 See the Git hooks documentation on [`prepare-commit-msg` hooks][prepare-commit-msg-docs] for details on how this works.
 
 [prepare-commit-msg-docs]: https://git-scm.com/docs/githooks#_prepare_commit_msg
+
+## Drawbacks
+
+If additional hooks are used (e.g. pre-commit) that prevent a commit from being created,
+the message has to be created from scratch when commiting again.

hooks/prepare-commit-msg.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+COMMIT_MSG_FILE=$1
+exec < /dev/tty && cz commit --dry-run --write-message-to-file $COMMIT_MSG_FILE || true