How to Search with Git

Git offers several powerful options to search for commits or changes.

Find Files by Content Pattern: Git Grep

To search for a specific pattern in repository files, you can use the Git grep command.

git grep pattern


Pattern can be a regular expression.

By default Git grep searches in the current directory but you can pass a branch name or directory to search instead. Git grep has two advantages over the shell's grep command. First, it only searches tracked files so you get more relevant results. Secondly, the shell's grep command requires that you have all the source files you need to search locally. On the other had, Git grep can search any known branch whether it's checked out or not and whether it's local or remote.

git grep pattern remote/branch

Here we search a remote branch that doesn't exist in the local repository for a pattern.

Find Commits by Message Pattern: Git Log Grep

To find commits by a pattern in the message added with the commit, not the diff, use the --grep option for the git log command.

git log --grep='Fixing bug 103'


Find Commits by Diff: Pickaxe

To find commits using the actual diff the commit added you can use the -S option for the log command, which is known as pickaxe. Note there's no space after the -S.

git log -Skeyword
git log -Smethod()


Find Commit by Line: Blame

To find the commit id for each line in a file use the git blame command. This command will show the commit that added each line in the file. This is useful when trying to figure out which commit introduced a change.

git blame filename


Find Commit by Test: Bisect

Bisect is a binary search mode Git offers to find a commit that introduced a bug or problem by allowing the user to examine commits and specify whether the commit is good or bad until, using binary search, Git narrows down the search and finds the single commit needed. You are free to use whatever test needed to determine whether the commit you have is good or bad. This is useful when we are searching by functionality or behavior not a pattern.

Git needs to know the last known good commit to have a starting point for searching. Git also needs a bad commit which is by default HEAD.

git bisect start
git bisect bad
git bisect good HEAD~20

In the commands above, we tell Git to start bisect search. Then we specify HEAD as a bad commit and the commit 20 changes back as the last known good commit.

Now Git will start checking out commits and asking whether the commit is good or bad.

git bisect bad
git bisect bad
...
git bisect good
git bisect good
git bisect bad


Now bisect search ends and Git tells us exactly which commit introduced the first bad change.

Dangling Commits: Git Fsck

Finally, the commit we need might be dangling and thus not searchable by the above methods. A commit is considered dangling if it is not connected to the repo tree, meaning there is no path of changes that a user can use to see the commit or checkout its changes.

A commit that is disconnected from other objects is referenced by the reflog for a configurable period with a default of 90 days before it becomes dangling. After the reflog expiration for disconnected objects, the commit is garbage collected and becomes dangling.

To find dangling commits use the Git fsck command. If there are any dangling commits, they will be shown.

git fsck

If you find a dangling commit, you can see its content using the Git show command.

git show commit-hash-id

To see the diff:

git show -p commit-hash-id



References

• http://amazon.com/Version-Control-Git-collaborative-development/dp/1449316387
• https://git-scm.com/book/en/v2/Git-Tools-Searching

How to Release iOS Ad Hoc Beta Builds with Xcode

After you have a running app and you have done enough testing on your iPhone and your other iDevices, the next step before submitting to the AppStore is to test on as many devices as possible. This type of testing is usually called beta testing. Beta testing is crucial in developing a great mobile app because of generally two types of feedback given by beta testers:

1. Compatibility problems. Even though everything might be sweet and sublime on your iPhone or iPad, it might not be the case for every combination of device and iOS version. Beta testing with hardware/software diverse testers will uncover all or most of those problems.
2. General story/usability flaws. This category is not about bugs. It's about understanding what part was confusing to your beta users or what false assumptions did you make. Beta testing will help bring your assumptions and perspective inline with real users.

---

In this guide I will give the procedure for how to generate ad hoc builds that you can send to your beta testers to try. I could not find a single tutorial that covered all the related issues so I decided to write this. This procedure does not require registering in the iOS Developer Enterprise Program. All that is required is the standard iOS Developer Program. This guide was written using Xcode 4.2.

1. Ask your users for their device ID's and add them in the iOS Provisioning Portal. Testers can find their device ID's from iTunes or from Xcode in the Organizer window. Using TestFlight (more on that later) can also simplify getting device ID's from users. TestFlight will email the tester's device ID once he/she registers.
   
2. Create a Distribution Ad Hoc Provisioning profile in iOS Portal and select all the devices for the beta users.
   
3. Download the new provisioning profile and install it in Xcode by double-clicking it or dragging it into the Xcode icon. Keep this file handy because we will need upload it to the web along with the ipa file and allow users to download it. Select this provisioning profile for code signing for the Release version of your project and targets.
   




4. Select "iOS Device" from your build schemes. the Archive button is disabled when the Simulator is selected.
   
   
   
5. Add an Entitlements file. In Xcode 4.2 you cannot add an Entitlements file by going to File -> New -> New File --like previous versions. You must select your project in the top left corner then click on your main target. Then scroll all the way to the bottom and check the box for Enable Entitlements.
   
6. If you have more than one target in your project then you must select "Yes" for the Skip Install setting under Deployment for all targets other than your main project target. You will end up with multiple targets if you are linking to other projects or have unit tests.
   
7. From the main menu select Product --> Archive.
   
8. From the Organizer - Archives window press the button Share.
   
9. Select iOS App Store Package (.ipa) and the correct signing identity for your build. Then press Next.
   
10. Type into the Save As field on top the name you want to give the files. Check the box for Save for Enterprise Distribution on the bottom. Enter the URL where the file will be hosted without the file name. All you need is the URL up to the directory path. Add a title for your app then press Save.
    
11. You should now have generated two files, a .ipa file and a .plist file. All you have to do now is upload these two files to your website along with your provisioning file (from step 3) then link to them on a webpage like shown below. The ipa and plist file must be in the same directory and must have the same name except for the extension. Your users should install the provisioning file first then install the app.
    
    Another option is instead of simply hosting these files on your website, you can utilize a service like TestFlight for better tracking and user experience. Using TestFlight is easy and you can use the TestFlight SDK to allow the users to send feedback and track how long the testers used the app and so on. For more on TestFlight visit: https://testflightapp.com/
    
    

    
    <html>
    <head>
    <title>Install iOS App</title>
    </head>
    <body>
    
    
    <a href="My_Provisioning_Profile_Ad_Hoc.mobileprovision">Install Team Provisioning File</a>
    
    
    <a href="itms-services://?action=download-manifest&url=http://yourwebsite/betafolder/myFavAppName.plist">Install Application</a>
    
    
    </body>
    </html>
    

    
    

You should provide your testers with links to the provisioning profile (.mobileprovision) and IPA file as shown above. Instruct them to install the provisioning profile first. However you should look into TestFlight for better management and tracking. There, that should get you started with installing all your cool apps on your friends' devices before you hit the AppStore.

Use Doubly Linked Not Singly Linked Lists

If you're going to write a general use library and use a linked list, please make it doubly linked. I was recently working with the Box2d library which I have to say is a great physics engine. The engine maintains a linked list of what it calls Fixtures attached to each body. While I was trying to use this list I was shocked to find that it was a singly linked list. In other words the list only had a "next" pointer, no previous pointer.

Unless you have a good reason like tail-sharing I really don't see why someone would do that especially in a general opensource library that would be used in a broad range of applications. First off, before we go into the pros and cons of both designs let's briefly talk about linked lists. A linked list is a data structure used to store a group of data objects by connecting objects with a "link". The link is basically a pointer from one object to the next one, previous one, or both. If there's only one link it's called a singly linked list. If there's both a previous and a next link, it's called a doubly linked list. The best part about a linked list is that it's very cheap to add and remove objects. All we need to do is add a new link or remove a link and assign a pointer to a different object. The worst part about a linked list is random access. If we need to access an object that happens to be in the middle of the list, there's no way to reach that object but to traverse through all the objects before it or after it.

When designing software, we're supposed make libraries as flexible and general as reasonably possible. We already know that access is the main weakness of linked lists. The least we can do to make accessing objects a little easier is to make the list a doubly linked one. In the case of linked lists it's easy to see why someone might need to go backwards in a list. But even if it weren't so obvious, if adding something doesn't cost much and it satisfies a common use it should be done in a general purpose type of library.

Looking at the pros and cons of a singly and doubly linked list, it also makes more sense to make them doubly linked. The only pro of using singly linked lists is that it saves memory but all we're saving is a pointer which is about 32 or 64 bits per object. The con is being limited to traverse a list in only one direction. Singly linked lists also make it more challenging to delete objects. The pro of having a doubly linked list is that from any object in the list we can move in either direction. Also it's a lot easier to delete an object in a doubly linked list. The con of doubly linked lists is that we use a little more memory for the second pointer. However the additional memory (32 or 64 bits per object) used is insignificant. In terms of asymptotic notation, we're still using O(n) memory which means our memory usage is linear with respect to the number of objects.

The good news is that I was able to modify the list and make it doubly linked. Take home message: bi-linking = bi-winning.

throw vs throw ex: C# .NET Exceptions

There are a couple options to raise an exception again after it has been caught. One option is to raise the exception again by using the "throw exception" keyword like below:

try 
{
   ...//code that encounters an exception
}
catch (Exception ex)
{
   ...//exception handling code
   throw ex; //raise the exception again
}

The disadvantage in this way is that the original context of the exception is lost. There is no longer a meaningful call stack attached to the exception because it will contain the latest context from the newly added throw. If you plan to throw the exception in this matter you should wrap the original exception into another new more high level (application) exception. The new exception would add more high level info about the original exception.


The second option is to use the throw keyword alone with out passing the actual exception variable. This tells the .NET framework to throw the original exception without updating its context like below:

try 
{
   ...//code that encounters an exception
}
catch (Exception e)
{
   ...//exception handling code
   throw; //notice the exception e is omitted
}

This way should be used when the exception is trivial enough and the code is too small to require wrapping into another exception. Again the advantage here is that you maintain the original call stack so that any user of this code can track the cause of the exception.

It's worth noting that Java is different in this aspect and using "throw ex" in Java will retain the original stack trace.

Nearby Windows Phone 7 Reviews and Maps App

Nearby is a new Windows Phone 7 (WP7) app. The app can be downloaded here from the Windows Phone 7 app store.

Nearby shows the user nearby places automatically upon opening. The user can scroll through the list of nearby places and find more information on a location he is interested in. Information for a location includes phone, address, website, rating, and distance. You can see the directories where the location is found such as Yelp, Yahoo and CitySearch. Using Nearby, you can view the location's page on Yelp and other sources within the app. Browsing to the Yelp or Yahoo page for the business allows you to see reviews and more info.





With Nearby, you can find step-by-step directions to the location you are interested in. You can also navigate through the itinerary steps and see the steps on the map.





Nearby allows you to bookmark your favorite locations so that you can find them easily. You may also share a location with a friend via SMS text or email. Calling a place is as easy as touching the phone icon or phone number after selecting a business.





List of favorite places and businesses for easy access.



Find out more about Nearby at http://www.challengesolutions.net