add tests that show what happens with allow-lists and / in root (#1458)

Author: Byron

gix-dir/tests/fixtures/many.sh

@@ -351,3 +351,75 @@ git clone submodule multiple-submodules
   git submodule add ../submodule a/b
   git commit -m "add modules"
 )
+
+git init slash-in-root-and-negated
+(cd slash-in-root-and-negated
+  cat <<'EOF' >.gitignore
+/
+!file
+!*.md
+!.github
+!.github/**
+EOF
+  touch file readme.md
+  mkdir .github
+  touch .github/workflow.yml
+  git add .github readme.md .gitignore
+  git commit -m "init"
+)
+
+git init star-in-root-and-negated
+(cd star-in-root-and-negated
+  cat <<'EOF' >.gitignore
+*
+!file
+!.gitignore
+!*.md
+!.github
+!.github/**
+EOF
+  touch file readme.md
+  mkdir .github
+  touch .github/workflow.yml
+  git add .github readme.md .gitignore
+  git commit -m "init"
+)
+
+git init slash-in-subdir-and-negated
+(cd slash-in-subdir-and-negated
+  mkdir sub
+  (cd sub
+    cat <<'EOF' >.gitignore
+/
+!file
+!*.md
+!.github
+!.github/**
+EOF
+    touch file readme.md
+    mkdir .github
+    touch .github/workflow.yml
+    git add .github readme.md .gitignore
+    git commit -m "init"
+  )
+)
+
+git init star-in-subdir-and-negated
+(cd star-in-subdir-and-negated
+  mkdir sub
+  (cd sub
+    cat <<'EOF' >.gitignore
+*
+!file
+!.gitignore
+!*.md
+!.github
+!.github/**
+EOF
+    touch file readme.md
+    mkdir .github
+    touch .github/workflow.yml
+    git add .github readme.md .gitignore
+    git commit -m "init"
+  )
+)

gix-dir/tests/walk/mod.rs

@@ -4276,3 +4276,115 @@ fn type_mismatch_ignore_case_clash_file_is_dir() {
          If there was no special handling for this, it would have found the file (`d` in the index, icase), which would have been wrong."
     );
 }
+
+#[test]
+fn top_level_slash_with_negations() -> crate::Result {
+    for repo_name in ["slash-in-root-and-negated", "star-in-root-and-negated"] {
+        let root = fixture(repo_name);
+        let ((out, _root), entries) = collect(&root, None, |keep, ctx| walk(&root, ctx, options_emit_all(), keep));
+        assert_eq!(
+            out,
+            walk::Outcome {
+                read_dir_calls: 0,
+                returned_entries: entries.len(),
+                seen_entries: 1,
+            }
+        );
+        assert_eq!(
+            entries,
+            &[entry("", Ignored(Expendable), Directory)],
+            "This is wrong - the root can never be listed"
+        );
+
+        let ((out, _root), entries) = collect(&root, None, |keep, ctx| {
+            walk(
+                &root,
+                ctx,
+                walk::Options {
+                    for_deletion: Some(ForDeletionMode::FindRepositoriesInIgnoredDirectories),
+                    emit_tracked: false,
+                    ..options_emit_all()
+                },
+                keep,
+            )
+        });
+        assert_eq!(
+            out,
+            walk::Outcome {
+                read_dir_calls: 2,
+                returned_entries: entries.len(),
+                seen_entries: 5,
+            }
+        );
+        assert_eq!(
+            entries,
+            &[
+                entry_nokind(".git", Ignored(Expendable))
+                    .with_property(DotGit)
+                    .with_match(Always),
+                entry("file", Ignored(Expendable), File)
+            ],
+            "This is still wrong, but consistent within what it should do.\
+            Top-level `.git` should always be Pruned, even if ignored.\
+            Except for `file` which should be untracked."
+        );
+    }
+    Ok(())
+}
+
+#[test]
+fn subdir_slash_with_negations() -> crate::Result {
+    for repo_name in ["slash-in-subdir-and-negated", "star-in-subdir-and-negated"] {
+        let root = fixture(repo_name);
+        let ((out, _root), entries) = collect(&root, None, |keep, ctx| walk(&root, ctx, options_emit_all(), keep));
+        assert_eq!(
+            out,
+            walk::Outcome {
+                read_dir_calls: 3,
+                returned_entries: entries.len(),
+                seen_entries: 5,
+            }
+        );
+        assert_eq!(
+            entries,
+            &[
+                entry_nokind(".git", Pruned).with_property(DotGit).with_match(Always),
+                entry("sub/.github/workflow.yml", Tracked, File),
+                entry("sub/.gitignore", Tracked, File),
+                entry("sub/file", Untracked, File),
+                entry("sub/readme.md", Tracked, File),
+            ],
+            "subdirectory matches work as expected, also with a `/` which has no bearing."
+        );
+
+        let ((out, _root), entries) = collect(&root, None, |keep, ctx| {
+            walk(
+                &root,
+                ctx,
+                walk::Options {
+                    for_deletion: Some(ForDeletionMode::FindRepositoriesInIgnoredDirectories),
+                    emit_tracked: false,
+                    ..options_emit_all()
+                },
+                keep,
+            )
+        });
+        assert_eq!(
+            out,
+            walk::Outcome {
+                read_dir_calls: 3,
+                returned_entries: entries.len(),
+                seen_entries: 5,
+            }
+        );
+        assert_eq!(
+            entries,
+            &[
+                entry_nokind(".git", Pruned).with_property(DotGit).with_match(Always),
+                entry("sub/file", Untracked, File)
+            ],
+            "This is expected, and the `.git` top-level is pruned."
+        );
+    }
+    Ok(())
+}