fix(git): ignore prefix-sharing tags that are not versions

src/git/tags.rs

@@ -86,7 +86,9 @@ impl TagIndex {
         let floating = self.floating_tag_names(prefix);
         self.entries
             .iter()
-            .filter(|e| e.reachable && e.name.starts_with(prefix) && !floating.contains(&e.name))
+            .filter(|e| {
+                e.reachable && is_version_tag(&e.name, prefix) && !floating.contains(&e.name)
+            })
             .max_by_key(|e| e.time)
             .map(|e| e.name.clone())
     }
@@ -131,7 +133,9 @@ impl TagIndex {
         let floating = self.floating_tag_names(prefix);
         self.entries
             .iter()
-            .filter(|e| e.reachable && e.name.starts_with(prefix) && !floating.contains(&e.name))
+            .filter(|e| {
+                e.reachable && is_version_tag(&e.name, prefix) && !floating.contains(&e.name)
+            })
             .max_by_key(|e| e.time)
             .map(|e| e.commit_oid)
     }
@@ -149,7 +153,7 @@ impl TagIndex {
             .iter()
             .filter(|e| {
                 e.reachable
-                    && e.name.starts_with(prefix)
+                    && is_version_tag(&e.name, prefix)
                     && !is_prerelease_tag(&e.name, prefix)
                     && !floating.contains(&e.name)
             })
@@ -302,6 +306,18 @@ pub(super) fn floating_tag_names<'a>(
     floating
 }
 
+pub(super) fn is_version_tag(tag_name: &str, prefix: &str) -> bool {
+    let Some(rest) = tag_name.strip_prefix(prefix) else {
+        return false;
+    };
+    let rest = rest.strip_prefix('v').unwrap_or(rest);
+    let core = rest.split(['-', '+']).next().unwrap_or(rest);
+    !core.is_empty()
+        && core
+            .split('.')
+            .all(|part| !part.is_empty() && part.bytes().all(|b| b.is_ascii_digit()))
+}
+
 pub(super) fn is_prerelease_tag(tag_name: &str, prefix: &str) -> bool {
     let version_part = tag_name.strip_prefix(prefix).unwrap_or(tag_name);
     version_part.contains('-')
@@ -467,8 +483,7 @@ fn prefixed_tags(
         .flatten()
         .filter_map(|reference| {
             let name = String::from_utf8_lossy(reference.name().shorten()).into_owned();
-            name.starts_with(prefix)
-                .then(|| (name, reference.id().detach()))
+            is_version_tag(&name, prefix).then(|| (name, reference.id().detach()))
         })
         .collect();
     let floating = floating_tag_names(tags.iter().map(|(name, _)| name.as_str()), prefix);

src/git/tests.rs

@@ -2566,3 +2566,56 @@ fn tag_index_reads_sequential_tags() {
         Some("v3")
     );
 }
+
+#[test]
+fn prefix_sharing_tag_without_a_version_is_not_the_last_tag() {
+    let (dir, repo) = init_repo();
+    create_commit_in_repo(&repo, dir.path(), "a.txt", "feat: first");
+    create_lightweight_tag(&repo, "v1.0.0");
+    create_commit_in_repo(&repo, dir.path(), "b.txt", "feat!: breaking");
+    create_lightweight_tag(&repo, "vendor-sync");
+    create_commit_in_repo(&repo, dir.path(), "c.txt", "fix: third");
+    let v1 = git(dir.path(), &["rev-parse", "v1.0.0^{commit}"]);
+
+    let idx = TagIndex::build(&repo).unwrap();
+    let last = idx
+        .find_last_tag_commit("v", OrphanedTagStrategy::Warn)
+        .unwrap();
+    assert_eq!(last.to_string(), v1.trim());
+
+    let found = find_last_tag_name(&repo, "v", OrphanedTagStrategy::Warn).unwrap();
+    assert_eq!(found, Some("v1.0.0".to_string()));
+}
+
+#[test]
+fn tag_of_a_sibling_package_is_not_the_last_tag() {
+    let (dir, repo) = init_repo();
+    create_commit_in_repo(&repo, dir.path(), "a.txt", "feat: first");
+    create_lightweight_tag(&repo, "core-1.0.0");
+    create_commit_in_repo(&repo, dir.path(), "b.txt", "feat(core): second");
+    create_commit_in_repo(&repo, dir.path(), "c.txt", "chore: third");
+    create_lightweight_tag(&repo, "core-utils-1.0.1");
+    let first = git(dir.path(), &["rev-parse", "core-1.0.0^{commit}"]);
+
+    let idx = TagIndex::build(&repo).unwrap();
+    let last = idx
+        .find_last_tag_commit("core-", OrphanedTagStrategy::Warn)
+        .unwrap();
+    assert_eq!(last.to_string(), first.trim());
+}
+
+#[test]
+fn prerelease_and_v_prefixed_versions_still_count_as_tags() {
+    let (dir, repo) = init_repo();
+    create_commit_in_repo(&repo, dir.path(), "a.txt", "feat: first");
+    create_lightweight_tag(&repo, "pkg-v1.0.0");
+    create_commit_in_repo(&repo, dir.path(), "b.txt", "feat: second");
+    create_lightweight_tag(&repo, "pkg-v1.1.0-beta.1");
+    let beta = git(dir.path(), &["rev-parse", "pkg-v1.1.0-beta.1^{commit}"]);
+
+    let idx = TagIndex::build(&repo).unwrap();
+    let last = idx
+        .find_last_tag_commit("pkg-", OrphanedTagStrategy::Warn)
+        .unwrap();
+    assert_eq!(last.to_string(), beta.trim());
+}