get_repo_path: refactor path-allocation

diff --git a/setup.c b/setup.c
index 82c0cc2a13bfeae3ec364dce2438fb4c67e46a35..5f9f07dcdb059ad6aeac8d90ee18aedf56a8f85e 100644 (file)
--- 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,