1 files changed, 81 insertions, 0 deletions
diff --git a/setup.c b/setup.c
index 7086741e6c..98c6fd8ee4 100644
--- a/setup.c
+++ b/setup.c
@@ -1703,6 +1703,87 @@ void set_git_dir(const char *path, int make_realpath)
 	strbuf_release(&realpath);
 }
 
+const char *enter_repo(const char *path, unsigned flags)
+{
+	static struct strbuf validated_path = STRBUF_INIT;
+	static struct strbuf used_path = STRBUF_INIT;
+
+	if (!path)
+		return NULL;
+
+	if (!(flags & ENTER_REPO_STRICT)) {
+		static const char *suffix[] = {
+			"/.git", "", ".git/.git", ".git", NULL,
+		};
+		const char *gitfile;
+		int len = strlen(path);
+		int i;
+		while ((1 < len) && (path[len-1] == '/'))
+			len--;
+
+		/*
+		 * We can handle arbitrary-sized buffers, but this remains as a
+		 * sanity check on untrusted input.
+		 */
+		if (PATH_MAX <= len)
+			return NULL;
+
+		strbuf_reset(&used_path);
+		strbuf_reset(&validated_path);
+		strbuf_add(&used_path, path, len);
+		strbuf_add(&validated_path, path, len);
+
+		if (used_path.buf[0] == '~') {
+			char *newpath = interpolate_path(used_path.buf, 0);
+			if (!newpath)
+				return NULL;
+			strbuf_attach(&used_path, newpath, strlen(newpath),
+				      strlen(newpath));
+		}
+		for (i = 0; suffix[i]; i++) {
+			struct stat st;
+			size_t baselen = used_path.len;
+			strbuf_addstr(&used_path, suffix[i]);
+			if (!stat(used_path.buf, &st) &&
+			    (S_ISREG(st.st_mode) ||
+			    (S_ISDIR(st.st_mode) && is_git_directory(used_path.buf)))) {
+				strbuf_addstr(&validated_path, suffix[i]);
+				break;
+			}
+			strbuf_setlen(&used_path, baselen);
+		}
+		if (!suffix[i])
+			return NULL;
+		gitfile = read_gitfile(used_path.buf);
+		if (!(flags & ENTER_REPO_ANY_OWNER_OK))
+			die_upon_dubious_ownership(gitfile, NULL, used_path.buf);
+		if (gitfile) {
+			strbuf_reset(&used_path);
+			strbuf_addstr(&used_path, gitfile);
+		}
+		if (chdir(used_path.buf))
+			return NULL;
+		path = validated_path.buf;
+	}
+	else {
+		const char *gitfile = read_gitfile(path);
+		if (!(flags & ENTER_REPO_ANY_OWNER_OK))
+			die_upon_dubious_ownership(gitfile, NULL, path);
+		if (gitfile)
+			path = gitfile;
+		if (chdir(path))
+			return NULL;
+	}
+
+	if (is_git_directory(".")) {
+		set_git_dir(".", 0);
+		check_repository_format(NULL);
+		return path;
+	}
+
+	return NULL;
+}
+
 static int git_work_tree_initialized;
 
 /*