commit b9995ddd0473f88cf6a56fc096a416e397969acf
Author: larstvei <larstvei@ifi.uio.no>
Date:   Thu Nov 13 23:20:08 2014 +0100

    Initial commit.

diff --git a/README.md b/README.md
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--- /dev/null
+++ b/README.md
@@ -0,0 +1,11 @@
+#try.el
+
+This is a package that allow you to try out other Emacs packages, without
+installing them. If you install a package (using `package-install`) you have
+to remember to delete this, if you realize you don't need that package. A
+common way around this is to copy the code into the `*scratch*`-buffer and
+evaluate the buffer. This extension essentially automates this process, by
+excepting a URL to a plain-text `.el`-file, downloading the content and
+evaluate it.
+
+Too bad you won't be able to try out `try.el` with `try.el`.
diff --git a/try.el b/try.el
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+++ b/try.el
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+;;; -*- lexical-binding: t -*-
+(require 'package)
+(require 'url)
+
+(defvar try-tmp-dir "/tmp/")
+
+(defun try-newest-package-installed-p (package)
+  "Return true if the newest available PACKAGE is installed."
+  (when (package-installed-p package)
+    (let* ((local-pkg-desc (or (assq package package-alist)
+                               (assq package package--builtins)))
+           (newest-pkg-desc (assq package package-archive-contents)))
+      (and local-pkg-desc newest-pkg-desc
+           (version-list-= (package-desc-vers (cdr local-pkg-desc))
+                           (package-desc-vers (cdr newest-pkg-desc)))))))
+
+
+(defun try-raw-link-p (url)
+  (string-match-p "[^:]*://\\([^?\r\n]+\\).*\.el?$" url))
+
+(defun try-raw-link (url)
+  (with-current-buffer (url-retrieve-synchronously url)
+    (condition-case nil
+        (progn
+          (eval-region (search-forward-regexp "^$") (point-max))
+          (message "Trying!"))
+      ((debug error)
+       (message "Could not parse %s" url) nil))))
+
+(defun try-compose (f g)
+  (lambda (&rest x) (funcall f (apply g x))))
+
+(defun try-package (package)
+  (unless package--initialized
+    (package-initialize t))
+  (unless package-archive-contents
+    (package-refresh-contents))
+  (if (try-newest-package-installed-p package)
+      (message "Already installed.")
+    (message "Trying %s!" (symbol-name package))
+    t))
+
+(defun try ()
+  "Takes an URL to a .el-file, and evaluates it."
+  (interactive)
+  (let ((url-or-package (completing-read
+                         "url or package: "
+                         (mapcar (try-compose 'symbol-name 'car)
+                                 package-archive-contents))))
+    (cond ((try-raw-link-p url-or-package) (try-raw-link url-or-package))
+          ((try-package (intern url-or-package)))
+          (t (message "Couldn't find a sensible way to try this.")))))
+
+(provide 'try)