Emacs Tip #1

Emacs is a great editor, I won't elaborate on this as there's countless blog posts already celebrating its countless features. After some years of usage, anyone using Emacs end up with a bloated .emacs file that may contains some good tips. I'll be explaining some of the tricks I'm using in a series of posts of which this one is the first.

Web Search Shortcuts

It's a known fact (in the sense that it's a common Intertubes meme) that some people use their computer exclusively through Emacs. I'm not that fond of this editor and prefer to do things like navigating the web with a real browser. Emacs as a way to send URLs to one, using the browse-url function. Feeding an unencoded URL to it could yield a bad request though. To fix that, we can use url-hexify-string from the url library. Here's a simple example of putting these functions to good use.

(require 'url)

(defun google ()
  (interactive)
  (let ((url (if (and transient-mark-mode mark-active)
               (buffer-substring-no-properties
                 (region-beginning)
                 (region-end))
               (thing-at-point 'symbol))))
    (browse-url
      (concat "http://www.google.com/search?"
        (format "q=%s" (url-hexify-string url))))))

This interactive function let us do a simple search with the text under the currently active region or with the symbol found under the cursor if there's no active region. This can be useful, you're no longer forced to copy-paste text from Emacs to your browser.

Next, we could try to send more complex queries to our preferred search engine, which in this case is Google. Standard library documentation such as Java's API specification generally have URLs that are easily queryable. With Google's allinurl keyword, we can make a function to search for a specific class symbol.

(defun search-all-in-url (query site inurl)
  (concat "http://www.google.com/"
    (format "search?q=allinurl:%s+site:%s+inurl:%s&btnI"
      (url-hexify-string query)
      (url-hexify-string site)
      (url-hexify-string inurl))))

(defun web-help (site inurl)
  (browse-url (search-all-in-url (thing-at-point 'symbol) site inurl)))

With web-help, we can now define custom interactive functions. Currently in my .emacs file, I've got two such functions, one for Java and the other for Ruby.

(defun java-help ()
  (interactive)
  (web-help "java.sun.com" "/javase/6/docs/api/"))

(defun ruby-help ()
  (interactive)
  (web-help "www.ruby-doc.org" "/core/"))

Then, it's a simple matter of adding key bindings for our new interactive functions. Personally, I like to have them bound to the lower F* keys.

(global-set-key [(f1)] 'google)
(global-set-key [(f2)] 'java-help)
(global-set-key [(f3)] 'ruby-help)

You might already use these shortcuts for other things (I think that F3 serves to start recording macros) but you certainly still have some unbound key combinations!

Update: I've corrected the second code example that I messed up while writing this post.

Git Tip #1

Changing Filename Case Under Cygwin

When using Git on Windows XP, you're confronted with a basic problem, case changes aren't accounted for while renaming files as Windows internals doesn't have a clue about the difference between lower and upper case. You can actually change the casing, but you can't have two files using the same name with different casing for example. This behavior obviously affect Git, which cannot detect filename case changes.

$ git init Initialized empty Git repository in /home/budu/tmp/.git/

$ touch foo

$ git add .

$ git commit -m 'test' [master (root-commit) 5a1fbb3] test 0 files
changed, 0 insertions(+), 0 deletions(-) create mode 100644 fo

$ mv foo FOO

$ l total 0 drwxr-xr-x+ 1 budu None 0 Jan 11 18:15 .git/ -rw-r--r-- 1
budu None 0 Jan 11 17:59 FOO

$ git status # On branch master nothing to commit (working directory
clean)

This is an unfortunate situation which can be easily resolved by using a simple trick. The first thing you need to do is to copy the file you want to modify to a different temporary name. Then you must use git rm on the original file and finally rename the temporary file to the new name with changed casing.

$ cp FOO bar

$ git rm foo rm 'foo'

$ mv bar FOO

$ git add .

$ git status # On branch master # Changes to be committed: # (use "git
reset HEAD ..." to unstage) # # renamed: foo -> FOO #

One thing to note here is that when calling git rm you have to use the original file name if its casing is already changed.