This option allows for more fine-grained placement of the location
marker for code violating a custom rule, e.g.:
```swift
print("Hello world.")
^~~~~
```
for this `.swiftlint.yml`:
```yaml
custom_rules:
world_preceded_by_hello:
name: "World Preceded by Hello"
included: ".+\\.swift"
message: "The word World predeced by the word hello should be capitalised."
severity: warning
regex: "(?i:hello)\\s+(world)"
match_kinds: [string]
capture_group: 1
```
Pyry Jahkola
JP Simard
Paul Taykalo
Marcelo Fabri