Creating custom hook scripts in Git - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to make a Git hook script executable.

Git

chmod [1] .git/hooks/pre-commit

Drag options to blanks, or click blank then click option'

A+x

B-x

C-r

D+r

Attempts:

3 left

💡 Hint

Common Mistakes

Using -x instead of +x disables execute permission.

Using read permission flags like +r instead of execute.

The chmod +x command makes the hook script executable so Git can run it.

2fill in blank

medium

Complete the first line of a Git hook script to specify the shell interpreter.

Git

#![1]/sh

Drag options to blanks, or click blank then click option'

A/bin

B/usr

C/sbin

D/etc

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect interpreter paths like /usr/bin or /etc.

Omitting the shebang line.

The shebang #!/bin/sh tells the system to use the shell interpreter to run the script.

3fill in blank

hard

Fix the error in the Git hook script line that prevents commit if a file named TODO exists.

Git

if [ -f [1] ]; then
  echo "Please resolve TODOs before commit."
  exit 1
fi

Drag options to blanks, or click blank then click option'

A'TODO'

B"TODO"

CTODO

Dtodo

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around the file name inside the test brackets.

Using wrong file name case.

The file name should be unquoted in the test expression to correctly check if the file exists.

4fill in blank

hard

Fill both blanks to create a pre-commit hook that checks for 'TODO' in staged files and blocks commit.

Git

if git diff --cached | grep -q [1]; then
  echo [2]
  exit 1
fi

Drag options to blanks, or click blank then click option'

ATODO

B"Commit blocked: TODO found in files."

C"All clear."

DFIXME

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong search string in grep.

Printing a message that does not explain the block.

The script checks if any staged file contains 'TODO' and prints a blocking message if found.

5fill in blank

hard

Fill all three blanks to create a post-commit hook that logs the last commit message to a file.

Git

git log -1 --pretty=[1] > [2]
echo "Logged commit message to [3]"

Drag options to blanks, or click blank then click option'

A"%B"

Bcommit_message.log

D"%s"

Attempts:

3 left

💡 Hint

Common Mistakes

Using %s which only shows the commit subject.

Mismatching file names in redirection and echo message.

The git log command with --pretty=%B outputs the full commit message body. The output is redirected to a log file, and a confirmation message is printed.

Practice

1. What is the main purpose of creating a custom Git hook script?

easy

A. To delete branches remotely

B. To change the Git commit message manually

C. To create new Git repositories

D. To run scripts automatically at specific Git events

Solution

1. Step 1: Understand Git hooks

   Git hooks are scripts that run automatically at certain points in Git's workflow, like before a commit or after a push.

2. Step 2: Identify the purpose of custom hooks

   Custom hooks let you automate tasks or enforce rules during these Git events without manual intervention.

3. Final Answer:

   To run scripts automatically at specific Git events -> Option D

4. Quick Check:

   Git hooks = automatic scripts at Git events [OK]

Hint: Hooks run scripts automatically at Git events [OK]

Common Mistakes:

• Thinking hooks manually change commit messages
• Confusing hooks with branch deletion
• Assuming hooks create repositories

2. Which of the following is the correct way to make a Git hook script executable on Linux or macOS?

easy

A. chmod +x .git/hooks/pre-commit

B. git hook enable pre-commit

C. chmod 777 .git/hooks/pre-commit

D. git config hook.pre-commit true

Solution

1. Step 1: Understand file permissions for hooks

   Git hooks must be executable files to run automatically.

2. Step 2: Use the correct command to make a file executable

   The command chmod +x adds execute permission without changing other permissions.

3. Final Answer:

   chmod +x .git/hooks/pre-commit -> Option A

4. Quick Check:

   Make hook executable = chmod +x [OK]

Hint: Use chmod +x to make hook scripts executable [OK]

Common Mistakes:

• Using git commands that don't exist for hooks
• Setting overly permissive permissions like 777
• Trying to enable hooks via git config

3. Given this pre-commit hook script placed in .git/hooks/pre-commit and made executable:

#!/bin/sh
if git diff --cached --quiet; then
  echo "No changes staged for commit."
  exit 1
fi

What happens when you try to commit without staging any changes?

medium

A. The commit is blocked with message 'No changes staged for commit.'

B. The commit proceeds normally without any message

C. The commit is blocked with a syntax error

D. The commit proceeds but shows a warning

Solution

1. Step 1: Analyze the script logic

   The script checks if there are no staged changes using git diff --cached --quiet. If true, it prints a message and exits with code 1.

2. Step 2: Understand Git hook exit codes

   Exiting with code 1 in a pre-commit hook stops the commit process and shows the message.

3. Final Answer:

   The commit is blocked with message 'No changes staged for commit.' -> Option A

4. Quick Check:

   Exit 1 in pre-commit = block commit [OK]

Hint: Exit non-zero in pre-commit stops commit [OK]

Common Mistakes:

• Assuming commit proceeds despite exit 1
• Confusing staged vs unstaged changes
• Expecting syntax errors from correct shell script

4. You wrote this post-commit hook script but it does not run after commits:

#!/bin/sh
echo "Commit done!"

Which is the most likely reason?

medium

A. The script filename is incorrect

B. The script is not executable

C. Git hooks cannot echo messages

D. The script must be in the project root, not .git/hooks

Solution

1. Step 1: Check common hook issues

   Hooks must be executable files inside .git/hooks/ with correct names.

2. Step 2: Identify the most common cause

   Often, scripts don't run because they lack execute permission, even if named correctly.

3. Final Answer:

   The script is not executable -> Option B

4. Quick Check:

   Hooks must be executable to run [OK]

Hint: Make hook scripts executable with chmod +x [OK]

Common Mistakes:

• Placing scripts outside .git/hooks directory
• Assuming echo is not allowed in hooks
• Using wrong hook filenames

5. You want to create a custom Git hook that prevents commits if the commit message does not contain the word 'JIRA'. Which script placed in .git/hooks/commit-msg will achieve this?

hard

A. #!/bin/sh
if grep -q 'JIRA' "$1"; then
exit 1
fi

B. #!/bin/sh
grep 'JIRA' "$1" || echo "Commit message missing JIRA"

C. #!/bin/sh
if ! grep -q 'JIRA' "$1"; then
echo "Commit message must include 'JIRA'."
exit 1
fi

D. #!/bin/sh
echo "Checking commit message for JIRA"

Solution

1. Step 1: Understand commit-msg hook argument

   The commit message file path is passed as the first argument ($1) to the script.

2. Step 2: Check script logic for enforcing 'JIRA'

   #!/bin/sh if ! grep -q 'JIRA' "$1"; then echo "Commit message must include 'JIRA'." exit 1 fi uses grep -q to check if 'JIRA' is missing, then prints a message and exits with 1 to block the commit.

3. Step 3: Evaluate other options

   #!/bin/sh grep 'JIRA' "$1" || echo "Commit message missing JIRA" only echoes but does not block commit. #!/bin/sh if grep -q 'JIRA' "$1"; then exit 1 fi blocks if 'JIRA' is present (wrong logic). #!/bin/sh echo "Checking commit message for JIRA" just echoes without checks.

4. Final Answer:

   #!/bin/sh if ! grep -q 'JIRA' "$1"; then echo "Commit message must include 'JIRA'." exit 1 fi -> Option C

5. Quick Check:

   Exit 1 if 'JIRA' missing blocks commit [OK]

Hint: Use commit-msg hook with exit 1 to block bad messages [OK]

Common Mistakes:

• Not exiting with non-zero to block commit
• Checking for presence instead of absence
• Only printing message without blocking