make hotfix use a plus instead of minus (#32060)

packages/flutter_tools/lib/src/version.dart

@@ -572,7 +572,7 @@ class GitTagVersion {
   /// The Z in vX.Y.Z.
   final int z;
 
-  /// the F in vX.Y.Z-hotfix.F
+  /// the F in vX.Y.Z+hotfix.F
   final int hotfix;
 
   /// Number of commits since the vX.Y.Z tag.
@@ -586,7 +586,7 @@ class GitTagVersion {
   }
 
   static GitTagVersion parse(String version) {
-    final RegExp versionPattern = RegExp(r'^v([0-9]+)\.([0-9]+)\.([0-9]+)(?:-hotfix\.([0-9]+))?-([0-9]+)-g([a-f0-9]+)$');
+    final RegExp versionPattern = RegExp(r'^v([0-9]+)\.([0-9]+)\.([0-9]+)(?:\+hotfix\.([0-9]+))?-([0-9]+)-g([a-f0-9]+)$');
     final List<String> parts = versionPattern.matchAsPrefix(version)?.groups(<int>[1, 2, 3, 4, 5, 6]);
     if (parts == null) {
       printTrace('Could not interpret results of "git describe": $version');
@@ -601,11 +601,11 @@ class GitTagVersion {
       return '0.0.0-unknown';
     if (commits == 0) {
       if (hotfix != null)
-        return '$x.$y.$z-hotfix.$hotfix';
+        return '$x.$y.$z+hotfix.$hotfix';
       return '$x.$y.$z';
     }
     if (hotfix != null)
-      return '$x.$y.$z-hotfix.${hotfix + 1}-pre.$commits';
+      return '$x.$y.$z+hotfix.${hotfix + 1}-pre.$commits';
     return '$x.$y.${z + 1}-pre.$commits';
   }
 }

packages/flutter_tools/test/version_test.dart

@@ -394,8 +394,8 @@ void main() {
     expect(GitTagVersion.parse('v1.2.3-4-g$hash').frameworkVersionFor(hash), '1.2.4-pre.4');
     expect(GitTagVersion.parse('v98.76.54-32-g$hash').frameworkVersionFor(hash), '98.76.55-pre.32');
     expect(GitTagVersion.parse('v10.20.30-0-g$hash').frameworkVersionFor(hash), '10.20.30');
-    expect(GitTagVersion.parse('v1.2.3-hotfix.1-4-g$hash').frameworkVersionFor(hash), '1.2.3-hotfix.2-pre.4');
-    expect(GitTagVersion.parse('v7.2.4-hotfix.8-0-g$hash').frameworkVersionFor(hash), '7.2.4-hotfix.8');
+    expect(GitTagVersion.parse('v1.2.3+hotfix.1-4-g$hash').frameworkVersionFor(hash), '1.2.3+hotfix.2-pre.4');
+    expect(GitTagVersion.parse('v7.2.4+hotfix.8-0-g$hash').frameworkVersionFor(hash), '7.2.4+hotfix.8');
     expect(testLogger.traceText, '');
     expect(GitTagVersion.parse('x1.2.3-4-g$hash').frameworkVersionFor(hash), '0.0.0-unknown');
     expect(GitTagVersion.parse('v1.0.0-unknown-0-g$hash').frameworkVersionFor(hash), '0.0.0-unknown');