A reference is used in git to specify branches and tags. A
branch head is stored under the `$GIT_DIR/refs/heads` directory, and
-a tag is stored under the `$GIT_DIR/refs/tags` directory. git
-imposes the following rules on how references are named:
+a tag is stored under the `$GIT_DIR/refs/tags` directory (or, if refs
+are packed by `git gc`, as entries in the `$GIT_DIR/packed-refs` file).
+git imposes the following rules on how references are named:
. They can include slash `/` for hierarchical (directory)
grouping, but no slash-separated component can begin with a