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

src/git-command-manager.ts

@@ -37,7 +37,6 @@ export interface IGitCommandManager {
     options: {
       filter?: string
       fetchDepth?: number
-      fetchTags?: boolean
       showProgress?: boolean
     }
   ): Promise<void>
@@ -280,14 +279,13 @@ class GitCommandManager {
     options: {
       filter?: string
       fetchDepth?: number
-      fetchTags?: boolean
       showProgress?: boolean
     }
   ): Promise<void> {
     const args = ['-c', 'protocol.version=2', 'fetch']
-    if (!refSpec.some(x => x === refHelper.tagsRefSpec) && !options.fetchTags) {
-      args.push('--no-tags')
-    }
+    // Always use --no-tags for explicit control over tag fetching
+    // Tags are fetched explicitly via refspec when needed
+    args.push('--no-tags')
 
     args.push('--prune', '--no-recurse-submodules')
     if (options.showProgress) {

src/git-source-provider.ts

@@ -159,7 +159,6 @@ export async function getSource(settings: IGitSourceSettings): Promise<void> {
     const fetchOptions: {
       filter?: string
       fetchDepth?: number
-      fetchTags?: boolean
       showProgress?: boolean
     } = {}
 
@@ -182,12 +181,35 @@ export async function getSource(settings: IGitSourceSettings): Promise<void> {
       if (!(await refHelper.testRef(git, settings.ref, settings.commit))) {
         refSpec = refHelper.getRefSpec(settings.ref, settings.commit)
         await git.fetch(refSpec, fetchOptions)
+
+        // Verify the ref now matches. For branches, the targeted fetch above brings
+        // in the specific commit. For tags (fetched by ref), this will fail if
+        // the tag was moved after the workflow was triggered.
+        if (!(await refHelper.testRef(git, settings.ref, settings.commit))) {
+          throw new Error(
+            `The ref '${settings.ref}' does not point to the expected commit '${settings.commit}'. ` +
+              `The ref may have been updated after the workflow was triggered.`
+          )
+        }
       }
     } else {
       fetchOptions.fetchDepth = settings.fetchDepth
-      fetchOptions.fetchTags = settings.fetchTags
-      const refSpec = refHelper.getRefSpec(settings.ref, settings.commit)
+      const refSpec = refHelper.getRefSpec(
+        settings.ref,
+        settings.commit,
+        settings.fetchTags
+      )
       await git.fetch(refSpec, fetchOptions)
+
+      // For tags, verify the ref still points to the expected commit.
+      // Tags are fetched by ref (not commit), so if a tag was moved after the
+      // workflow was triggered, we would silently check out the wrong commit.
+      if (!(await refHelper.testRef(git, settings.ref, settings.commit))) {
+        throw new Error(
+          `The ref '${settings.ref}' does not point to the expected commit '${settings.commit}'. ` +
+            `The ref may have been updated after the workflow was triggered.`
+        )
+      }
     }
     core.endGroup()
 

src/ref-helper.ts

@@ -76,55 +76,75 @@ export function getRefSpecForAllHistory(ref: string, commit: string): string[] {
   return result
 }
 
-export function getRefSpec(ref: string, commit: string): string[] {
+export function getRefSpec(
+  ref: string,
+  commit: string,
+  fetchTags?: boolean
+): string[] {
   if (!ref && !commit) {
     throw new Error('Args ref and commit cannot both be empty')
   }
 
   const upperRef = (ref || '').toUpperCase()
+  const result: string[] = []
+
+  // When fetchTags is true, always include the tags refspec
+  if (fetchTags) {
+    result.push(tagsRefSpec)
+  }
 
   // SHA
   if (commit) {
     // refs/heads
     if (upperRef.startsWith('REFS/HEADS/')) {
       const branch = ref.substring('refs/heads/'.length)
-      return [`+${commit}:refs/remotes/origin/${branch}`]
+      result.push(`+${commit}:refs/remotes/origin/${branch}`)
     }
     // refs/pull/
     else if (upperRef.startsWith('REFS/PULL/')) {
       const branch = ref.substring('refs/pull/'.length)
-      return [`+${commit}:refs/remotes/pull/${branch}`]
+      result.push(`+${commit}:refs/remotes/pull/${branch}`)
     }
     // refs/tags/
     else if (upperRef.startsWith('REFS/TAGS/')) {
-      return [`+${commit}:${ref}`]
+      if (!fetchTags) {
+        result.push(`+${ref}:${ref}`)
+      }
     }
     // Otherwise no destination ref
     else {
-      return [commit]
+      result.push(commit)
     }
   }
   // Unqualified ref, check for a matching branch or tag
   else if (!upperRef.startsWith('REFS/')) {
-    return [
-      `+refs/heads/${ref}*:refs/remotes/origin/${ref}*`,
-      `+refs/tags/${ref}*:refs/tags/${ref}*`
-    ]
+    result.push(`+refs/heads/${ref}*:refs/remotes/origin/${ref}*`)
+    if (!fetchTags) {
+      result.push(`+refs/tags/${ref}*:refs/tags/${ref}*`)
+    }
   }
   // refs/heads/
   else if (upperRef.startsWith('REFS/HEADS/')) {
     const branch = ref.substring('refs/heads/'.length)
-    return [`+${ref}:refs/remotes/origin/${branch}`]
+    result.push(`+${ref}:refs/remotes/origin/${branch}`)
   }
   // refs/pull/
   else if (upperRef.startsWith('REFS/PULL/')) {
     const branch = ref.substring('refs/pull/'.length)
-    return [`+${ref}:refs/remotes/pull/${branch}`]
+    result.push(`+${ref}:refs/remotes/pull/${branch}`)
   }
   // refs/tags/
-  else {
-    return [`+${ref}:${ref}`]
+  else if (upperRef.startsWith('REFS/TAGS/')) {
+    if (!fetchTags) {
+      result.push(`+${ref}:${ref}`)
+    }
   }
+  // Other refs
+  else {
+    result.push(`+${ref}:${ref}`)
+  }
+
+  return result
 }
 
 /**
@@ -170,8 +190,10 @@ export async function testRef(
   // refs/tags/
   else if (upperRef.startsWith('REFS/TAGS/')) {
     const tagName = ref.substring('refs/tags/'.length)
+    // Use ^{commit} to dereference annotated tags to their underlying commit
     return (
-      (await git.tagExists(tagName)) && commit === (await git.revParse(ref))
+      (await git.tagExists(tagName)) &&
+      commit === (await git.revParse(`${ref}^{commit}`))
     )
   }
   // Unexpected