How to use the command `git annotate` (with examples)

The git annotate command is used to display commit hash and author information for each line of a file. It is similar to the git blame command, but is provided for users familiar with other version control systems. The above use cases illustrate different ways to use the git annotate command along with their corresponding code, motivations, explanations, and example outputs.

Use case 1: Print a file with the author name and commit hash prepended to each line

Code:

git annotate path/to/file

Motivation:

The motivation behind using this use case is to view the commit history and author information for each line of a file. By displaying the author name and commit hash before each line, it becomes easier to identify who made the changes and when.

Explanation:

• git annotate: This is the command itself.
• path/to/file: This specifies the path to the file for which the annotation is to be displayed.

Example output:

35e3ec8b (John Doe 2019-08-12 10:43:23) This is the first line of the file
35e3ec8b (John Doe 2019-08-12 10:43:23) This is the second line of the file
5afe8f19 (Jane Smith 2019-08-15 18:26:12) This is the third line of the file

Use case 2: Print a file with the author email and commit hash prepended to each line

Code:

git annotate -e path/to/file

Motivation:

The motivation behind using this use case is to view the commit history and author information for each line of a file, including the author email. This can be useful when multiple authors have the same name, but different email addresses.

Explanation:

• git annotate: This is the command itself.
• -e: This flag tells git annotate to include the author email in the output.
• path/to/file: This specifies the path to the file for which the annotation is to be displayed.

Example output:

35e3ec8b (John Doe <john.doe@gmail.com> 2019-08-12 10:43:23) This is the first line of the file
35e3ec8b (John Doe <john.doe@gmail.com> 2019-08-12 10:43:23) This is the second line of the file
5afe8f19 (Jane Smith <jane.smith@gmail.com> 2019-08-15 18:26:12) This is the third line of the file

Use case 3: Print only rows that match a regular expression

Code:

git annotate -L :regexp path/to/file

Motivation:

The motivation behind using this use case is to filter the output of git annotate and only display the lines that match a given regular expression. This can be useful when looking for specific changes or trying to analyze the commit history for certain patterns.

Explanation:

• git annotate: This is the command itself.
• -L :regexp: This flag tells git annotate to filter the output to only include lines that match the specified regular expression.
• path/to/file: This specifies the path to the file for which the annotation is to be displayed.

Example output:

5afe8f19 (Jane Smith 2019-08-15 18:26:12) This line contains the matching pattern

Conclusion:

The git annotate command is a useful tool for displaying commit history and author information on a per-line basis. By utilizing the different options provided, users can customize the output to suit their specific needs, whether it’s viewing the author name, email, or filtering based on a regular expression.