runs chdir to the toplevel of the working tree.
require_work_tree::
- checks if the repository is a bare repository, and dies
- if so. Used by scripts that require working tree
- (e.g. `checkout`).
+ checks if the current directory is within the working tree
+ of the repository, and otherwise dies.
+
+require_work_tree_exists::
+ checks if the working tree associated with the repository
+ exists, and otherwise dies. Often done before calling
+ cd_to_toplevel, which is impossible to do if there is no
+ working tree.
get_author_ident_from_commit::
outputs code for use with eval to set the GIT_AUTHOR_NAME,