Fix nil file name for buffer when projectile-cache-current-file

When opening a file from the terminal, it is possible for the
file to be a project and have the `switch-to-buffer` hook run,
with a new buffer that has no associated file.

CHANGELOG.md

@@ -21,11 +21,13 @@
 
 * Prefer ag's internal .gitignore parsing.
 * Always use external find-tag implementations.
+* When opening a specified file from the terminal, do not error inside of `projectile-cache-current-file`.
 
 ### Bugs fixed
 
 * [#871](https://github.com/bbatsov/projectile/issues/871): Stop advice for `compilation-find-file` to override other advices.
 * [#557](https://github.com/bbatsov/projectile/issues/557): stack overflow in `projectile-find-tag'.
+* [#957](https://github.com/bbatsov/projectile/pull/957): When opening a specified file from the terminal, do not error inside of `projectile-cache-current-file`.
 
 ## 0.13.0 (10/21/2015)
 

projectile.el

@@ -657,8 +657,8 @@ The cache is created both in memory and on the hard drive."
   "Add the currently visited file to the cache."
   (interactive)
   (let ((current-project (projectile-project-root)))
-    (when (gethash (projectile-project-root) projectile-projects-cache)
-      (let* ((abs-current-file (file-truename (buffer-file-name (current-buffer))))
+    (when (and (buffer-file-name) (gethash (projectile-project-root) projectile-projects-cache))
+      (let* ((abs-current-file (file-truename (buffer-file-name)))
             (current-file (file-relative-name abs-current-file current-project)))
       (unless (or (projectile-file-cached-p current-file current-project)
                   (projectile-ignored-directory-p (file-name-directory abs-current-file))