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# revision(_:)

Returns a requirement for a source control revision such as the hash of
a commit.

```
static func revision(_ ref: String) -> Package.Dependency.Requirement
```

## Parameters

`ref`

The Git revision, usually a commit hash.

## Discussion

Note that packages that use commit-based dependency requirements can’t
be depended upon by packages that use version-based dependency
requirements; you should remove commit-based dependency requirements
before publishing a version of your package.

The following example defines a version requirement for a specific
commit hash.

```swift
.revision(“e74b07278b926c9ec6f9643455ea00d1ce04a021”)
```

---

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