you only have two working trees, at "/abc/def/ghi" and "/abc/def/ggg",
then "ghi" or "def/ghi" is enough to point to the former working tree.
+REFS
+----
+In multiple working trees, some refs may be shared between all working
+trees, some refs are local. One example is HEAD is different for all
+working trees. This section is about the sharing rules and how to access
+refs of one working tree from another.
+
+In general, all pseudo refs are per working tree and all refs starting
+with "refs/" are shared. Pseudo refs are ones like HEAD which are
+directly under GIT_DIR instead of inside GIT_DIR/refs. There are one
+exception to this: refs inside refs/bisect and refs/worktree is not
+shared.
+
+Refs that are per working tree can still be accessed from another
+working tree via two special paths, main-worktree and worktrees. The
+former gives access to per-worktree refs of the main working tree,
+while the latter to all linked working trees.
+
+For example, main-worktree/HEAD or main-worktree/refs/bisect/good
+resolve to the same value as the main working tree's HEAD and
+refs/bisect/good respectively. Similarly, worktrees/foo/HEAD or
+worktrees/bar/refs/bisect/bad are the same as
+GIT_COMMON_DIR/worktrees/foo/HEAD and
+GIT_COMMON_DIR/worktrees/bar/refs/bisect/bad.
+
+To access refs, it's best not to look inside GIT_DIR directly. Instead
+use commands such as linkgit:git-rev-parse[1] or linkgit:git-update-ref[1]
+which will handle refs correctly.
+
+CONFIGURATION FILE
+------------------
+By default, the repository "config" file is shared across all working
+trees. If the config variables `core.bare` or `core.worktree` are
+already present in the config file, they will be applied to the main
+working trees only.
+
+In order to have configuration specific to working trees, you can turn
+on "worktreeConfig" extension, e.g.:
+
+------------
+$ git config extensions.worktreeConfig true
+------------
+
+In this mode, specific configuration stays in the path pointed by `git
+rev-parse --git-path config.worktree`. You can add or update
+configuration in this file with `git config --worktree`. Older Git
+versions will refuse to access repositories with this extension.
+
+Note that in this file, the exception for `core.bare` and `core.worktree`
+is gone. If you have them in $GIT_DIR/config before, you must move
+them to the `config.worktree` of the main working tree. You may also
+take this opportunity to review and move other configuration that you
+do not want to share to all working trees:
+
+ - `core.worktree` and `core.bare` should never be shared
+
+ - `core.sparseCheckout` is recommended per working tree, unless you
+ are sure you always use sparse checkout for all working trees.
+
DETAILS
-------
Each linked working tree has a private sub-directory in the repository's
`/path/other/test-next/.git/HEAD` or `/path/main/.git/HEAD`) while `git
rev-parse --git-path refs/heads/master` uses
$GIT_COMMON_DIR and returns `/path/main/.git/refs/heads/master`,
-since refs are shared across all working trees.
+since refs are shared across all working trees, except refs/bisect and
+refs/worktree.
See linkgit:gitrepository-layout[5] for more information. The rule of
thumb is do not make any assumption about whether a path belongs to
`test-next` entry from being pruned. See
linkgit:gitrepository-layout[5] for details.
+When extensions.worktreeConfig is enabled, the config file
+`.git/worktrees/<id>/config.worktree` is read after `.git/config` is.
+
LIST OUTPUT FORMAT
------------------
The worktree list command has two output formats. The default format shows the