checkout: support checking out into a new working directory

diff --git a/Documentation/git.txt b/Documentation/git.txt
index afb48d39bbd229bb0a28d2e7e2fb835e63248525..0c2dcfa9cc4f3cc3e3066104ee5a61f0b46fcfde 100644 (file)
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -809,6 +809,15 @@ Git so take care if using Cogito etc.
        an explicit repository directory set via 'GIT_DIR' or on the
        command line.
 
+'GIT_COMMON_DIR'::
+       If this variable is set to a path, non-worktree files that are
+       normally in $GIT_DIR will be taken from this path
+       instead. Worktree-specific files such as HEAD or index are
+       taken from $GIT_DIR. See linkgit:gitrepository-layout[5] and
+       the section 'MULTIPLE CHECKOUT MODE' in linkgit:checkout[1]
+       details. This variable has lower precedence than other path
+       variables such as GIT_INDEX_FILE, GIT_OBJECT_DIRECTORY...
+
 Git Commits
 ~~~~~~~~~~~
 'GIT_AUTHOR_NAME'::