Generate GitRevision.swift for inclusion in an Xcode project

generate-git-revision.sh

#!/usr/bin/env bash

set -euo pipefail

cat <<SWIFT
//
//  GitRevision.swift
//
//  This file was automatically generated. Do not edit manually. It will be overwritten on every build.
//
//  IMPORTANT: This file must be added to .gitignore or it will dirty the working tree every time there is a build.
//

/// Information about the current Git revision.
struct GitRevision {

    /// The name of the current branch.
    static let branch = "$(git rev-parse --abbrev-ref HEAD)"

    /// The abbreviated hash of the current commit.
    static let commit = "$(git rev-parse --short HEAD)"

    /// Whether the working tree is clean. If false, indicates that there are uncommitted or untracked files in the working tree.
    static let clean = $([[ -z $(git status -s) ]] && echo 'true' || echo 'false')

    /// Build timestamp. Set when this file was generated at the beginning of the build process.
    static let timestamp = "$(date +%Y-%m-%dT%H:%M:%S)"

    /// A string summarizing the current Git revision.
    static var description: String {
        return "\(commit)\(clean ? "" : "-dirty") \(branch) \(timestamp)"
    }
}
SWIFT