Add elpa packages

elpa/nix-mode-1.5.0/nix-log.el

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+;;; nix-log.el --- Run nix commands -*- lexical-binding: t -*-
+
+;; Author: Matthew Bauer <mjbauer95@gmail.com>
+;; Homepage: https://github.com/NixOS/nix-mode
+;; Package-Requires: ((emacs "24.1"))
+;; Keywords: nix
+
+
+;; This file is NOT part of GNU Emacs.
+
+;;; Commentary:
+
+;;; Code:
+
+(require 'nix)
+(require 'nix-instantiate)
+(require 'files)
+
+(defun nix-log-path (drv-file)
+  "Get the nix log of path a derivation"
+  (let* ((drv-name (file-relative-name drv-file nix-store-dir))
+	 (log-file (format "%s/log/nix/drvs/%s/%s.bz2"
+                           nix-state-dir
+                           (substring drv-name 0 2) (substring drv-name 2))))
+    (if (file-exists-p log-file) log-file
+      (error "No log is available for derivation"))))
+
+;;;###autoload
+(defun nix-log (file attr)
+  "Open the nix log.
+FILE nix file to parse.
+ATTR attribute to load the log of."
+  (interactive (list (nix-read-file) nil))
+  (unless attr (setq attr (nix-read-attr file)))
+
+  (let* ((drv-file (nix-instantiate file attr))
+         (log-file (nix-log-path drv-file)))
+    (find-file log-file)))
+
+(provide 'nix-log)
+;;; nix-log.el ends here