Add platform-independent .git "symlink"

This patch allows .git to be a regular textfile containing the path of
the real git directory (prefixed with "gitdir: "), which can be useful on
platforms lacking support for real symlinks.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/setup.c b/setup.c
index 3d2d9580f3..53580fde43 100644
--- a/setup.c
+++ b/setup.c
@@ -315,6 +315,44 @@ static int check_repository_format_gently(int *nongit_ok)
 }
 
 /*
+ * Try to read the location of the git directory from the .git file,
+ * return path to git directory if found.
+ */
+const char *read_gitfile_gently(const char *path)
+{
+	char *buf;
+	struct stat st;
+	int fd;
+	size_t len;
+
+	if (stat(path, &st))
+		return NULL;
+	if (!S_ISREG(st.st_mode))
+		return NULL;
+	fd = open(path, O_RDONLY);
+	if (fd < 0)
+		die("Error opening %s: %s", path, strerror(errno));
+	buf = xmalloc(st.st_size + 1);
+	len = read_in_full(fd, buf, st.st_size);
+	close(fd);
+	if (len != st.st_size)
+		die("Error reading %s", path);
+	buf[len] = '\0';
+	if (prefixcmp(buf, "gitdir: "))
+		die("Invalid gitfile format: %s", path);
+	while (buf[len - 1] == '\n' || buf[len - 1] == '\r')
+		len--;
+	if (len < 9)
+		die("No path in gitfile: %s", path);
+	buf[len] = '\0';
+	if (!is_git_directory(buf + 8))
+		die("Not a git repository: %s", buf + 8);
+	path = make_absolute_path(buf + 8);
+	free(buf);
+	return path;
+}
+
+/*
  * We cannot decide in this function whether we are in the work tree or
  * not, since the config can only be read _after_ this function was called.
  */
@@ -323,6 +361,7 @@ const char *setup_git_directory_gently(int *nongit_ok)
 	const char *work_tree_env = getenv(GIT_WORK_TREE_ENVIRONMENT);
 	static char cwd[PATH_MAX+1];
 	const char *gitdirenv;
+	const char *gitfile_dir;
 	int len, offset;
 
 	/*
@@ -377,8 +416,10 @@ const char *setup_git_directory_gently(int *nongit_ok)
 
 	/*
 	 * Test in the following order (relative to the cwd):
+	 * - .git (file containing "gitdir: <path>")
 	 * - .git/
 	 * - ./ (bare)
+	 * - ../.git
 	 * - ../.git/
 	 * - ../ (bare)
 	 * - ../../.git/
@@ -386,6 +427,12 @@ const char *setup_git_directory_gently(int *nongit_ok)
 	 */
 	offset = len = strlen(cwd);
 	for (;;) {
+		gitfile_dir = read_gitfile_gently(DEFAULT_GIT_DIR_ENVIRONMENT);
+		if (gitfile_dir) {
+			if (set_git_dir(gitfile_dir))
+				die("Repository setup failed");
+			break;
+		}
 		if (is_git_directory(DEFAULT_GIT_DIR_ENVIRONMENT))
 			break;
 		if (is_git_directory(".")) {