# Viewing the evolution of a line or function

`git log`'s `-L` flag allows us to trace the evolution of a single line, a range of lines, or a function.

## Line range

To view the history of a range of lines, specify `<start>:<end>` following `-L`:

```bash
git log -L5,15:pom.xml
```

To view a single line, use the same line number for both `<start>` and `<end>`:

```bash
git log -L9,9:pom.xml
```

## Function

To view the history of a function, specify `:<funcname>` following `-L`, where `<funcname>` is a regular expression.

```bash
git log -L:getUserById:path/to/my/Class.java
```

From the `git-log` manpage:

> The function names are determined in the same way as git diff works out patch hunk headers

This is, by default:

> ... a line that begins with an alphabet, an underscore or a dollar sign

This won't be approriate in many cases, particularly not in Java where methods are members of classes, meaning they are indented. The default funcname regex does not match any lines with leading whitespace. To change how hunk headers are determined, we need to update `.gitattributes` within the project:

```
*.java  diff=java
```

We can define a custom regular expression that suits our purposes, but there are a few built-in patterns to make this easier, and `java` is one of them, so we're all set.

Source:

* `LESS='-p Defining a custom hunk-header' man gitattributes`
* `LESS='-p -L<start>' man git-log`


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://notes.eliasnorrby.com/git/evolution-of-a-line-or-function.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.