Category Archives: Programming

GIT merge-svn

How to use GIT to merge two SVN branches

TL;DR: Download the git-merge-svn script here

I’ve been using git for years now but had to start using SVN for some projects. I found that GIT is good enough Subversion client too, especially as I retain the ability to commit often and rebase my work on top of commits from other devs (on the SVN side).

The only question arose – can I merge two SVN branches so that GIT log will show the merge?

The git-svn manual states that one should avoid all git clone|merge|pull|push activity when using git-svn.

But git log does show merge history that was created in Subversion – how does it do that?


Subversion does not support actual merge of branches (more like cherry-picking), but since version 1.5 Subversion supports the svn:mergeinfo property that is used to track what has been merged into this folder previously.

Digging some more into the matter, I found out that GIT supports setting svn:mergeinfo property on the SVN branch when dcommit‘ing:

git svn dcommit --mergeinfo "/branches/somebranch:1-3"

NB! the svn:mergeinfo is overwritten with whatever is given on the command-line, so be careful to list previous merges too.

While more recent git version added the config parameter to automatically set this property:

config key: svn.pushmergeinfo

I had some troubles with the automatic mergeinfo – for one reason or the other GIT calculated it wrong and I couldn’t get it to work.

SOLUTION: git-merge-svn

To automate the process, I wrote a shell script git merge-svn which can be used to merge two SVN branches with correct svn:mergeinfo set on the dcommit.

The script handles both situations:

  • the branch is not merged in git – will do git merge beforehand
  • the branches have been already merged in git (but not in SVN) – will traverse until previous ancestor for the merged commit revisions.

Download the git-merge-svn script here

Example usage

With this script I was able to produce these merges solely on git-side and retain the merge info so that GIT graph shows the log nicely:

git-merge-svn result

  1. Make some commits on devel6
  2. dcommit devel6 to SVN (required to get SVN revision numbers for the commits)
  3. check out testtunk6 – yes, I know I made a typo in the name ;-)
  4. git merge-svn devel6

The last commant outputs:

% git merge-svn devel6
About to do an SVN merge: devel6 -> testtunk6

| * devel6 [7b71187] (r102)
* | testtunk6 [0682a45] (r101)
  * [273d6d6] (r100)

STEP 1: GIT merge
  git merge devel6

Continue? (y/n) [n]: y
Merge made by the 'recursive' strategy.
 testfile | 1 +
 1 file changed, 1 insertion(+)

STEP 2: SVN dcommit

git svn dcommit --mergeinfo
/idp/branches/devel:9-32,35-41 /idp/branches/devel6:89 /idp/branches/devel6:94 /idp/branches/devel6:93 /idp/branches/devel6:96 /idp/branches/devel6:97 /idp/branches/devel6:99 /idp/branches/devel6:100 /idp/branches/devel6:102

Continue? (y/n) [n]: y
Committing to ...
  M testfile
Committed r103
  M testfile
Found merge parent (svn:mergeinfo prop): 7b71187fc371d3f86658c5850009e63be88157ac
r103 = 87759323cbadd38bac78087d57b6870a926287e7 (refs/remotes/svn/testtunk6)
No changes between 3fb2168cfbbe605fbd810d76513443203a85a549 and refs/remotes/svn/testtunk6
Resetting to the latest refs/remotes/svn/testtunk6

Safari New Window

Safari New Window icon

Previously I have written AppleScripts to open new windows for TextMate, Sublime Text 2 and also Safari. But the latter was somehow corrupt when using with Mac OS X 10.8.3, so I rewrote it based on previous two, adding features in the process:

  1. Checks if Safari is already running and creates new window (without switching spaces)
  2. Activates Safari if it’s not running yet.

The full source code is here:

-- quickly check if app is running.
-- Thanks
on appIsRunning(appName)
    tell application "System Events" to (name of processes) contains appName
end appIsRunning

property appName : "Safari"

-- Open new windows or If app is not already running, start it
if appIsRunning(appName) then
    tell application appName
        make new document
    end tell
    tell application appName to activate
end if

Go a head and download the updated script here:


Download Safari New Window  


Rails redirect_back_or_default

In a recent project I found myself writing recirect_to :back alot, and then found myself worrying that what if for some reason there is no :back.

Drawing inspiration from this blog, I wrote two helpers in my application_controller.rb.

The store_location stores current URI (or referer URI in case of non-GET request) into session[:return_to] for later usage:

def store_location
  session[:return_to] = if request.get?

And redirect_back_or_default tries its best to redirect the user to somewhere, in the following order:

  1. previously stored session[:return_to]
  2. Referer URI
  3. Given default URI
  4. or root_url if all else fails

The code itself

def redirect_back_or_default(default = root_url, options)
  redirect_to(session.delete(:return_to) || request.referer || default, options)

I’ve found that when rewriting redirect_to :back, notice: 'something' into redirect_back_or_default-call, adding this alias helps:

alias_method :redirect_to_back_or_default, :redirect_back_or_default

But of course, if you are testing your code (and you should be), it’s better to stick to one variant of above and use tests to catch all erroneous incarnations.

Rails 3: Merge scopes

I run into a case where I had method and I wanted the GroupMember model be searchable by the user’s attributes. The most DRY way to accomplish this in Rails 3 is to merge scopes. In the User model:

# user.rb
class User < ActiveRecord::Base
  has_many :memberships, :class_name => "GroupMember", :foreign_key => "user_id"

    if search.present?
      query = []
      params = []
      %w(uid email name).each do |field|
        # The field name must be fully qualified to merge scopes
        query << "#{self.table_name}.#{field} LIKE ?"
        params << "%#{search}%"
      query = query.join(" OR ")
      where(query, *params)

NB! It’s important to have the User’s field names fully qualified so that they won’t be applied to the GroupMember table. And in the GroupMember model:

# group_member.rb
class GroupMember < ActiveRecord::Base
  belongs_to :user
  belongs_to :group

    if search.present?
      # We search GroupMembers by the user attributes

Now it’s possible to search for GroupMembers by the User attributes:

group = Group.find 1'david')

This results in SQL query:

SELECT "group_members".* FROM "group_members" INNER JOIN "users"
ON "users"."id" = "group_members"."user_id" WHERE "group_members"."group_id" = 1
AND (users.uid LIKE '%david%' OR LIKE '%david%'
OR LIKE '%david%')

Sublime Text 2 New Window (via AppleScript)

Building upon my older post on opening new window in Text Mate 2, I now threw together small script to do the same in Sublime Text 2.

While Sublime Text 2 is superb text editor, it is not Mac native, thus it’s even less probable that a new Mac-style Dock icon menu will appear in near future, that allows opening new window quickly. Thus a helper application is in order.


Based on the original TMNewWindow code, only small modifications were needed. One unexpected behavior was with detecting working state of the application. For whatever reason the original script gave errors when run against Sublime Text 2.

Again, the AppleScript application is linked below and feel free to send me updates and patches if needed.



uses of Ruby’s Object#tap

Ruby 1.9′s Object#tap method has always seemed useful to me, but until now I hadn’t met the chance to use it. Every other time it seemed like abusing it in some way.

Now I came to an old code. Consider this:

cgi.text_field( "name" => "myfield",
                "value" => value,
                "size" => 20,
                "maxlength" => maxlength

I needed to turn that maxlength into a conditional attribute (omiting it if it’s nil).
One way would have been extracting the attributes into a separate variable:

attrs = {
          "name" => "myfield",
          "value" => value,
          "size" => 20
attrs['maxlength'] = maxlength if maxlength
cgi.text_field( attrs )

But this separates visually the cgi.text_field() call from it’s arguments, which I don’t like. Tap to the resque:

cgi.text_field({  "name" => "myfield",
                  "value" => value,
                  "size" => 20
                  attrs['maxlength'] = maxlength if maxlength

Now, isn’t that nice! (OK, maybe it isn’t, but at least it is encompassed in the method call and makes it easy to spot all attributes).

Restore DBD::MySQL::Database#quote method

For whatever reason, Ruby DBI and DBD have axed the quote method from their midst, breaking compatibility with previous versions. Sadly I couldn’t find any clues as to why it was removed (actually, bluntly commented out).

Fortunately I was able to unearth some hints how to restore this method and with an added fix to NilClass, the result seems to be working fine:

# For some unknown reason quote method is commented out at:
# Restoring it for b/w compliance
module DBI::DBD::Mysql
  class Database < DBI::BaseDatabase
    def quote(value)
        case value
        when String
        when DBI::Binary
        when TrueClass
        when FalseClass
        when Array
          value.collect { |v| quote(v) }.join(", ")
        when DBI::Date, DBI::Time, DBI::Timestamp, ::Date
        when ::Time
        when NilClass

Just place this in some file and require it in your code.


Mount partitions like a boss (AppleScript)

How to quickly mount partitions when the need arises? A small AppleScript to help you out.

The need

No good comes without little drawbacks. When I swapped ODD with HDD, I noticed that it was quite a bit noisier than SSD and even compared to similar MBP with HDD in original bay (probably because ODD bay has a slot that lets noise out easily). So, now I tend to eject the secondary disk when I don’t need it, so my Mac can spin it down. All nice and dandy, but reattaching it when needed was a bit tedious.

The Script

set partList to {"Meedia", "BOOTCAMP"}
choose from list partList with prompt "Choose partitions" with multiple selections allowed
if result is not equal to false then
	repeat with part in result
		do shell script "diskutil mount " & part
		display dialog "Volume " & part & " mounted"
	end repeat
end if

This script asks for which of the partitions to mount and then iterates with diskutil through the selection.


You can copy-paste the above script to AppleScript Editor and adjust it to your needs, or you can download this as a ready to use application.


Ruby (on Rails) toolchest for Windows users

Setting up solid Ruby on Rails developer box based on Windows can be tedious task. More so than on other platforms, because vanilla Windows is meant for end user and lacks proper development tools that exist on other platforms. But fear not, there are many good people out there that have jumped through multitude of hoops to get different parts of the ecosystem working. All that remains is to build a solid foundation for developmer from them. Read more »

TextMate 2 New Window (via AppleScript)

Often I find myself in a situation where I need to quickly paste some text and edit it a bit. Switching to TextMate also switches spaces to my last TM session, which might not be my current space. With other programs (and TextMate 1 for that matter) this can be overcome by selecting “New file” or “New window” from dock menu.

But the problem is that TextMate 2 alpha currently does not have
“New file” option in the Dock menu. I really miss this, because of my workflow – I use spaces to manage projects and programs I have open concurrently and I don’t want to mix the TextMate windows between spaces. So opening new TM2 window in current space is a must.

But surely the developers are preoccupied with more important features and thus I decided to throw in my 2 cents and cobbled together an AppleScript that one can use to open new window in current space.


Place this script in your Applications folder and wait until Spotlight has indexed it. Then push whatever shortcut you have for Spotlight (or Alfred, if you are like me) and enter few first chars. I have found that tmn is enough to trigger this application.

Hitting enter will fire this app and a sec later new TextMate window should be opened in current space. Definitely faster than switching to TM2, hitting ⌘N and then moving the window to correct space.


▼ Download TMNewWindow