these aren't explained elsewhere, I believe they will be confusing

Author: schacon

book/11-git-internals/sections/environment.asc

@@ -38,8 +38,6 @@ If this isn't specified, Git walks up the directory tree until it gets to `~` or
 *`GIT_CEILING_DIRECTORIES`* controls the behavior of searching for a `.git` directory.
 If you access directories that are slow to load (such as those on a tape drive, or across a slow network connection), you may want to have Git stop trying earlier than it might otherwise, especially if Git is invoked when building your shell prompt.
 
-*`GIT_DISCOVERY_ACROSS_FILESYSTEM`* can be used to allow Git to cross filesystem boundaries when searching for a `.git` directory (the default behavior is not to cross the boundary).
-
 *`GIT_WORK_TREE`* is the location of the root of the working directory for a non-bare repository.
 If not specified, the parent directory of `$GIT_DIR` is used.
 
@@ -50,8 +48,6 @@ If not specified, the parent directory of `$GIT_DIR` is used.
 *`GIT_ALTERNATE_OBJECT_DIRECTORIES`* is a colon-separated list (formatted like `/dir/one:/dir/two:…`) which tells Git where to check for objects if they aren't in `GIT_OBJECT_DIRECTORY`.
 If you happen to have a lot of projects with large files that have the exact same contents, this can be used to avoid storing too many copies of them.
 
-*`GIT_SHALLOW_FILE`* overrides the default location of the ``shallow'' file, which usually lives at `.git/shallow`.
-
 
 ==== Pathspecs