Add support for GIT_ONE_FILESYSTEM

This patch makes git pay attention to the GIT_ONE_FILESYSTEM environment
variable. When that variable is set, git will stop searching for a
GIT_DIR when it attempts to cross a filesystem boundary.

When working in an environment with too many automount points to make
maintaining a GIT_CEILING_DIRECTORIES list enjoyable, GIT_ONE_FILESYSTEM
gives the option of turning all such attempts off with one setting.

Signed-off-by: Lars R. Damerow <lars@pixar.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 31 insertions, 0 deletions

diff --git a/Documentation/git.txt b/Documentation/git.txt
index 4e00b315ff..bf1b45eef1 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -530,6 +530,12 @@ git so take care if using Cogito etc.
 	a GIT_DIR set on the command line or in the environment.
 	(Useful for excluding slow-loading network directories.)
 
+'GIT_ONE_FILESYSTEM'::
+	If set to a true value ("true" or a non-zero integer), stop at
+	filesystem boundaries when looking for a repository directory.
+	Like 'GIT_CEILING_DIRECTORIES', it will not affect an explicit
+	respository directory set via 'GIT_DIR' or on the command line.
+
 git Commits
 ~~~~~~~~~~~
 'GIT_AUTHOR_NAME'::
diff --git a/setup.c b/setup.c
index f0b56b9f54..8b911b1a38 100644
--- a/setup.c
+++ b/setup.c
@@ -323,6 +323,8 @@ const char *setup_git_directory_gently(int *nongit_ok)
 	const char *gitdirenv;
 	const char *gitfile_dir;
 	int len, offset, ceil_offset, root_len;
+	int current_device = 0, one_filesystem = 0;
+	struct stat buf;
 
 	/*
 	 * Let's assume that we are in a git repository.
@@ -390,6 +392,12 @@ const char *setup_git_directory_gently(int *nongit_ok)
 	 *   etc.
 	 */
 	offset = len = strlen(cwd);
+	one_filesystem = git_env_bool("GIT_ONE_FILESYSTEM", 0);
+	if (one_filesystem) {
+		if (stat(".", &buf))
+			die_errno("failed to stat '.'");
+		current_device = buf.st_dev;
+	}
 	for (;;) {
 		gitfile_dir = read_gitfile_gently(DEFAULT_GIT_DIR_ENVIRONMENT);
 		if (gitfile_dir) {
@@ -422,6 +430,23 @@ const char *setup_git_directory_gently(int *nongit_ok)
 			}
 			die("Not a git repository (or any of the parent directories): %s", DEFAULT_GIT_DIR_ENVIRONMENT);
 		}
+		if (one_filesystem) {
+			if (stat("..", &buf)) {
+				cwd[offset] = '\0';
+				die_errno("failed to stat '%s/..'", cwd);
+			}
+			if (buf.st_dev != current_device) {
+				if (nongit_ok) {
+					if (chdir(cwd))
+						die_errno("Cannot come back to cwd");
+					*nongit_ok = 1;
+					return NULL;
+				}
+				cwd[offset] = '\0';
+				die("Not a git repository (or any parent up to mount parent %s)\n"
+					"Stopping at filesystem boundary since GIT_ONE_FILESYSTEM is set.", cwd);
+			}
+		}
 		if (chdir("..")) {
 			cwd[offset] = '\0';
 			die_errno("Cannot change to '%s/..'", cwd);