1 files changed, 69 insertions, 20 deletions

diff --git a/setup.c b/setup.c
index 82c0cc2a13..5f9f07dcdb 100644
--- a/setup.c
+++ b/setup.c
@@ -411,35 +411,58 @@ static void update_linked_gitdir(const char *gitfile, const char *gitdir)
 /*
  * Try to read the location of the git directory from the .git file,
  * return path to git directory if found.
+ *
+ * On failure, if return_error_code is not NULL, return_error_code
+ * will be set to an error code and NULL will be returned. If
+ * return_error_code is NULL the function will die instead (for most
+ * cases).
  */
-const char *read_gitfile(const char *path)
+const char *read_gitfile_gently(const char *path, int *return_error_code)
 {
-	char *buf;
-	char *dir;
+	const int max_file_size = 1 << 20;  /* 1MB */
+	int error_code = 0;
+	char *buf = NULL;
+	char *dir = NULL;
 	const char *slash;
 	struct stat st;
 	int fd;
 	ssize_t len;
 
-	if (stat(path, &st))
-		return NULL;
-	if (!S_ISREG(st.st_mode))
-		return NULL;
+	if (stat(path, &st)) {
+		error_code = READ_GITFILE_ERR_STAT_FAILED;
+		goto cleanup_return;
+	}
+	if (!S_ISREG(st.st_mode)) {
+		error_code = READ_GITFILE_ERR_NOT_A_FILE;
+		goto cleanup_return;
+	}
+	if (st.st_size > max_file_size) {
+		error_code = READ_GITFILE_ERR_TOO_LARGE;
+		goto cleanup_return;
+	}
 	fd = open(path, O_RDONLY);
-	if (fd < 0)
-		die_errno("Error opening '%s'", path);
+	if (fd < 0) {
+		error_code = READ_GITFILE_ERR_OPEN_FAILED;
+		goto cleanup_return;
+	}
 	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);
+	if (len != st.st_size) {
+		error_code = READ_GITFILE_ERR_READ_FAILED;
+		goto cleanup_return;
+	}
 	buf[len] = '\0';
-	if (!starts_with(buf, "gitdir: "))
-		die("Invalid gitfile format: %s", path);
+	if (!starts_with(buf, "gitdir: ")) {
+		error_code = READ_GITFILE_ERR_INVALID_FORMAT;
+		goto cleanup_return;
+	}
 	while (buf[len - 1] == '\n' || buf[len - 1] == '\r')
 		len--;
-	if (len < 9)
-		die("No path in gitfile: %s", path);
+	if (len < 9) {
+		error_code = READ_GITFILE_ERR_NO_PATH;
+		goto cleanup_return;
+	}
 	buf[len] = '\0';
 	dir = buf + 8;
 
@@ -453,15 +476,41 @@ const char *read_gitfile(const char *path)
 		free(buf);
 		buf = dir;
 	}
-
-	if (!is_git_directory(dir))
-		die("Not a git repository: %s", dir);
-
+	if (!is_git_directory(dir)) {
+		error_code = READ_GITFILE_ERR_NOT_A_REPO;
+		goto cleanup_return;
+	}
 	update_linked_gitdir(path, dir);
 	path = real_path(dir);
 
+cleanup_return:
+	if (return_error_code)
+		*return_error_code = error_code;
+	else if (error_code) {
+		switch (error_code) {
+		case READ_GITFILE_ERR_STAT_FAILED:
+		case READ_GITFILE_ERR_NOT_A_FILE:
+			/* non-fatal; follow return path */
+			break;
+		case READ_GITFILE_ERR_OPEN_FAILED:
+			die_errno("Error opening '%s'", path);
+		case READ_GITFILE_ERR_TOO_LARGE:
+			die("Too large to be a .git file: '%s'", path);
+		case READ_GITFILE_ERR_READ_FAILED:
+			die("Error reading %s", path);
+		case READ_GITFILE_ERR_INVALID_FORMAT:
+			die("Invalid gitfile format: %s", path);
+		case READ_GITFILE_ERR_NO_PATH:
+			die("No path in gitfile: %s", path);
+		case READ_GITFILE_ERR_NOT_A_REPO:
+			die("Not a git repository: %s", dir);
+		default:
+			assert(0);
+		}
+	}
+
 	free(buf);
-	return path;
+	return error_code ? NULL : path;
 }
 
 static const char *setup_explicit_git_dir(const char *gitdirenv,