Enable lenient parsing of Git version tags

- Git version tags will now be parsed leniently, allowing for tags like 2.0 to be treated equivelently to 2.0.0.
- Previous behavior was that a tag without a v-prefix would be preferred over one with a v-prefix. This behavior was maintained.
- A tag with more version components is preferred. 2.0.0 will be preferred over 2.0.

Sources/Basics/Version+Extensions.swift

@@ -16,9 +16,9 @@ extension Version {
     /// - Parameter tag: A version string possibly prepended with "v".
     public init?(tag: String) {
         if tag.first == "v" {
-            self.init(string: String(tag.dropFirst()))
+            try? self.init(versionString: String(tag.dropFirst()), usesLenientParsing: true)
         } else {
-            self.init(string: tag)
+            try? self.init(versionString: tag, usesLenientParsing: true)
         }
     }
 }

Sources/PackageGraph/RepositoryPackageContainer.swift

@@ -96,9 +96,23 @@ public class RepositoryPackageContainer: PackageContainer, CustomStringConvertib
             let knownVersionsWithDuplicates = Git.convertTagsToVersionMap(try repository.getTags())
 
             return knownVersionsWithDuplicates.mapValues({ tags -> String in
-                if tags.count == 2 {
+                if tags.count > 1 {
                     // FIXME: Warn if the two tags point to different git references.
-                    return tags.first(where: { !$0.hasPrefix("v") })!
+
+                    // If multiple tags are present with the same semantic version (e.g. v1.0.0, 1.0.0, 1.0) reconcile which one we prefer.
+                    // Prefer the most specific tag, e.g. 1.0.0 is preferred over 1.0.
+                    // Sort the tags so the most specific tag is first, order is ascending so the most specific tag will be last
+                    let tagsSortedBySpecificity = tags.sorted {
+                        let componentCounts = ($0.components(separatedBy: ".").count, $1.components(separatedBy: ".").count)
+                        if componentCounts.0 == componentCounts.1 {
+                            //if they are both have the same number of components, favor the one without a v prefix.
+                            //this matches previously defined behavior
+                            //this assumes we can only enter this situation because one tag has a v prefix and the other does not.
+                            return $0.hasPrefix("v")
+                        }
+                        return componentCounts.0 < componentCounts.1
+                    }
+                    return tagsSortedBySpecificity.last!
                 }
                 assert(tags.count == 1, "Unexpected number of tags")
                 return tags[0]

Tests/PackageGraphTests/RepositoryPackageContainerProviderTests.swift

@@ -341,6 +341,12 @@ class RepositoryPackageContainerProviderTests: XCTestCase {
         try repo.commit()
         try repo.tag(name: "v1.0.0")
         try repo.tag(name: "1.0.0")
+        try repo.tag(name: "v1.1.0")
+        try repo.tag(name: "1.1.0")
+        try repo.tag(name: "1.1")
+        try repo.tag(name: "1.2")
+        try repo.tag(name: "1.3")
+        try repo.tag(name: "1.3.0")
         try repo.tag(name: "1.0.1")
         try repo.tag(name: "v1.0.2")
         try repo.tag(name: "1.0.4")
@@ -366,7 +372,7 @@ class RepositoryPackageContainerProviderTests: XCTestCase {
         let ref = PackageReference.remote(identity: PackageIdentity(path: repoPath), location: repoPath.pathString)
         let container = try provider.getContainer(for: ref, skipUpdate: false)
         let v = try container.toolsVersionsAppropriateVersionsDescending().map { $0 }
-        XCTAssertEqual(v, ["2.0.1", "1.0.4", "1.0.2", "1.0.1", "1.0.0"])
+        XCTAssertEqual(v, ["2.0.1", "1.3.0", "1.2.0", "1.1.0", "1.0.4", "1.0.2", "1.0.1", "1.0.0"])
     }
 
     func testDependencyConstraints() throws {