Separate commit details from changed files

TESTING.md

@@ -230,11 +230,12 @@ xcrun simctl launch booted de.rfc1437.gotcha
       branch whose tip was deleted.
 - [ ] Open a commit and verify its header shows the full title and description,
       full hash, author, committer, date, known branch/ref, and signature status
-      above the Changed Files paths and statuses. Unsigned commits say
+      above the Changed Files paths and statuses, with a thin system separator
-      **Unsigned**. Verify paragraphs, lists, links, and inline styles in a
+      between the header and first file. Unsigned commits say **Unsigned**.
-      multi-line commit description use the repository file Preview Markdown
+      Verify paragraphs, lists, links, and inline styles in a multi-line commit
-      presentation. Check that long values wrap and remain readable at the
+      description use the repository file Preview Markdown presentation. Check
-      largest Dynamic Type accessibility size.
+      that long values wrap and remain readable at the largest Dynamic Type
+      accessibility size.
 - [ ] Open a changed file and verify the diff title, old/new line numbers,
       monospaced text, addition/removal/hunk colors, vertical scrolling, and
       source-style horizontal scrolling for long lines without word wrapping,

ios/Sources/DetailScreens.swift

@@ -403,6 +403,7 @@ private final class CommitHeaderView: UIView {
     private let titleLabel = UILabel()
     private var descriptionView: UIView?
     private let metadataStack = UIStackView()
+    private let bottomSeparator = separator()
 
     override init(frame: CGRect) {
         super.init(frame: frame)
@@ -422,11 +423,16 @@ private final class CommitHeaderView: UIView {
         stack.addArrangedSubview(titleLabel)
         stack.addArrangedSubview(metadataStack)
         addSubview(stack)
+        bottomSeparator.translatesAutoresizingMaskIntoConstraints = false
+        addSubview(bottomSeparator)
         NSLayoutConstraint.activate([
             stack.leadingAnchor.constraint(equalTo: layoutMarginsGuide.leadingAnchor),
             stack.trailingAnchor.constraint(equalTo: layoutMarginsGuide.trailingAnchor),
             stack.topAnchor.constraint(equalTo: layoutMarginsGuide.topAnchor),
             stack.bottomAnchor.constraint(equalTo: layoutMarginsGuide.bottomAnchor),
+            bottomSeparator.leadingAnchor.constraint(equalTo: leadingAnchor),
+            bottomSeparator.trailingAnchor.constraint(equalTo: trailingAnchor),
+            bottomSeparator.bottomAnchor.constraint(equalTo: bottomAnchor),
         ])
     }