tpope/vim-fugitive — pull request #431 by jrib (2014-01-21 23:45:43+00:00)
Title: Respect GIT_CEILING_DIRECTORIES, see git(1).

From git(1):

GIT_CEILING_DIRECTORIES
This should be a colon-separated list of absolute paths. If set, it is a list of directories that Git
should not chdir up into while looking for a repository directory (useful for excluding slow-loading
network directories). It will not exclude the current working directory or a GIT_DIR set on the command
line or in the environment. Normally, Git has to read the entries in this list and resolve any symlink
that might be present in order to compare them with the current directory. However, if even this access
is slow, you can add an empty entry to the list to tell Git that the subsequent entries are not symlinks
and needn’t be resolved; e.g., GIT_CEILING_DIRECTORIES=/maybe/symlink::/very/slow/non/symlink.

This patch currently does not duplicate git's behavior of resolving symlinks.