Fix tag handling: preserve annotations and explicit fetch-tags (#2356)

This PR fixes several issues with tag handling in the checkout action:

1. fetch-tags: true now works (fixes #1471)
   - Tags refspec is now included in getRefSpec() when fetchTags=true
   - Previously tags were only fetched during a separate fetch that was
     overwritten by the main fetch

2. Tag checkout preserves annotations (fixes #290)
   - Tags are fetched via refspec (+refs/tags/*:refs/tags/*) instead of
     --tags flag
   - This fetches the actual tag objects, preserving annotations

3. Tag checkout with fetch-tags: true no longer fails (fixes #1467)
   - When checking out a tag with fetchTags=true, only the wildcard
     refspec is used (specific tag refspec is redundant)

Changes:
- src/ref-helper.ts: getRefSpec() now accepts fetchTags parameter and
  prepends tags refspec when true
- src/git-command-manager.ts: fetch() simplified to always use --no-tags,
  tags are fetched explicitly via refspec
- src/git-source-provider.ts: passes fetchTags to getRefSpec()
- Added E2E test for fetch-tags option

Related #1471, #1467, #290

__test__/ref-helper.test.ts

@@ -152,7 +152,22 @@ describe('ref-helper tests', () => {
   it('getRefSpec sha + refs/tags/', async () => {
     const refSpec = refHelper.getRefSpec('refs/tags/my-tag', commit)
     expect(refSpec.length).toBe(1)
-    expect(refSpec[0]).toBe(`+${commit}:refs/tags/my-tag`)
+    expect(refSpec[0]).toBe(`+refs/tags/my-tag:refs/tags/my-tag`)
+  })
+
+  it('getRefSpec sha + refs/tags/ with fetchTags', async () => {
+    // When fetchTags is true, only include tags wildcard (specific tag is redundant)
+    const refSpec = refHelper.getRefSpec('refs/tags/my-tag', commit, true)
+    expect(refSpec.length).toBe(1)
+    expect(refSpec[0]).toBe('+refs/tags/*:refs/tags/*')
+  })
+
+  it('getRefSpec sha + refs/heads/ with fetchTags', async () => {
+    // When fetchTags is true, include both the branch refspec and tags wildcard
+    const refSpec = refHelper.getRefSpec('refs/heads/my/branch', commit, true)
+    expect(refSpec.length).toBe(2)
+    expect(refSpec[0]).toBe('+refs/tags/*:refs/tags/*')
+    expect(refSpec[1]).toBe(`+${commit}:refs/remotes/origin/my/branch`)
   })
 
   it('getRefSpec sha only', async () => {
@@ -168,6 +183,14 @@ describe('ref-helper tests', () => {
     expect(refSpec[1]).toBe('+refs/tags/my-ref*:refs/tags/my-ref*')
   })
 
+  it('getRefSpec unqualified ref only with fetchTags', async () => {
+    // When fetchTags is true, skip specific tag pattern since wildcard covers all
+    const refSpec = refHelper.getRefSpec('my-ref', '', true)
+    expect(refSpec.length).toBe(2)
+    expect(refSpec[0]).toBe('+refs/tags/*:refs/tags/*')
+    expect(refSpec[1]).toBe('+refs/heads/my-ref*:refs/remotes/origin/my-ref*')
+  })
+
   it('getRefSpec refs/heads/ only', async () => {
     const refSpec = refHelper.getRefSpec('refs/heads/my/branch', '')
     expect(refSpec.length).toBe(1)
@@ -187,4 +210,21 @@ describe('ref-helper tests', () => {
     expect(refSpec.length).toBe(1)
     expect(refSpec[0]).toBe('+refs/tags/my-tag:refs/tags/my-tag')
   })
+
+  it('getRefSpec refs/tags/ only with fetchTags', async () => {
+    // When fetchTags is true, only include tags wildcard (specific tag is redundant)
+    const refSpec = refHelper.getRefSpec('refs/tags/my-tag', '', true)
+    expect(refSpec.length).toBe(1)
+    expect(refSpec[0]).toBe('+refs/tags/*:refs/tags/*')
+  })
+
+  it('getRefSpec refs/heads/ only with fetchTags', async () => {
+    // When fetchTags is true, include both the branch refspec and tags wildcard
+    const refSpec = refHelper.getRefSpec('refs/heads/my/branch', '', true)
+    expect(refSpec.length).toBe(2)
+    expect(refSpec[0]).toBe('+refs/tags/*:refs/tags/*')
+    expect(refSpec[1]).toBe(
+      '+refs/heads/my/branch:refs/remotes/origin/my/branch'
+    )
+  })
 })