Change full ref path to avoid conflicts

This can cause some conflicts if the given ref is refs/heads/main, for example. In that case, we can't write refs/copybara_fetch/refs/heads/main/copybara_full_reference.

This changes this code to save the ref to `refs/copybara_fetch/refs/heads/main_copybara_full_reference`. (note that we are not adding `copybara_full_reference` as a path component, but just as a suffix with an underscore separator.

BUG=380307584
PiperOrigin-RevId: 730997697
Change-Id: Ic3244000efc5fdedc8c4b270a26fe6b64f42700e

Author: chris-campos

Diff for: java/com/google/copybara/git/GitRepository.java

@@ -169,7 +169,7 @@ public class GitRepository {
   public static final String GIT_DESCRIBE_ABBREV = "GIT_DESCRIBE_ABBREV";
   public static final String GIT_TAG_POINTS_AT = "GIT_TAG_POINTS_TO";
   public static final String HTTP_PERMISSION_DENIED = "The requested URL returned error: 403";
-  public static final String FULL_REF_NAMESPACE = "copybara_full_ref";
+  public static final String FULL_REF_NAMESPACE = "_copybara_full_ref";
   public static final String COPYBARA_FETCH_NAMESPACE = "refs/copybara_fetch";
 
   /**
@@ -418,7 +418,7 @@ public GitRevision fetchSingleRefWithTags(
           .addAll(refspec.build())
           .add(
               String.format(
-                  "refs/*/%s:%s/refs/*/%s/%s",
+                  "refs/*/%s:%s/refs/*/%s%s",
                   ref, COPYBARA_FETCH_NAMESPACE, ref, FULL_REF_NAMESPACE));
 
       try {

Diff for: java/com/google/copybara/git/GitRevision.java

@@ -149,7 +149,10 @@ public Optional<String> fullReference() {
     } else {
       try {
         ImmutableList<String> matchingRefs =
-            repository.showRef(ImmutableList.of(reference, FULL_REF_NAMESPACE)).entrySet().stream()
+            repository
+                .showRef(ImmutableList.of(reference, reference + FULL_REF_NAMESPACE))
+                .entrySet()
+                .stream()
                 .filter(e -> e.getKey().startsWith(COPYBARA_FETCH_NAMESPACE + "/refs/"))
                 .filter(e -> e.getValue().getSha1().equals(sha1))
                 .map(Entry::getKey)
@@ -181,9 +184,8 @@ private static String getCleanedFullReference(String originalRef) {
     if (fullRef.startsWith(prefix)) {
       fullRef = fullRef.substring(prefix.length());
     }
-    String suffix = "/" + FULL_REF_NAMESPACE;
-    if (fullRef.endsWith(suffix)) {
-      fullRef = fullRef.substring(0, fullRef.length() - suffix.length());
+    if (fullRef.endsWith(FULL_REF_NAMESPACE)) {
+      fullRef = fullRef.substring(0, fullRef.length() - FULL_REF_NAMESPACE.length());
     }
 
     return fullRef;

Diff for: javatests/com/google/copybara/git/GitRepositoryTest.java

@@ -911,7 +911,7 @@ public FetchResult fetch(
                 ImmutableList.of(
                     "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa:refs/copybara_fetch/aaaaaaaaaa"
                         + "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
-                    "refs/*/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa:refs/copybara_fetch/refs/*/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/copybara_full_ref"),
+                    "refs/*/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa:refs/copybara_fetch/refs/*/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_copybara_full_ref"),
                 ImmutableList.of(
                     "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa:refs/copybara_fetch/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa")));
   }