change repo branch

[BrianLitwin]

#2162

additions:

• A change-repository-branch workflow thats very similar to the workflow in Milestones
• GraphQL query to fetch a repo's branches

modifications:

• a mutable "branch" string in RepositoryOverviewController and RepositoryCodeDirectoryViewController
• updated the V3RepositoryReadME fetch to include a branch parameter
• a protocol RepositoryBranchUpdatable to flag and update the appropriate ViewControllers when a user switches branches
• ContextMenu and UIAlertAction setup
• Removed some outdated code to get a repo's branch name from fetch(page:) in RepositoryOverviewViewController
• Added a line feed.adapter.reloadData() in fetch(page:) because app was crashing intermittently after a user switched branches without that line - was always an IGListKit duplicate identifier error on StyledTextRenderers - to reproduce, remove the feed.adapter.reloadData(), go to https://github.com/TheAlgorithms/Python, try to switch branches and the app will crash. I'm working raising an issue for it.

[rnystrom]

Love this! So excited to play with it. Couple notes from me.

[rnystrom]

We'll need to find another solution for this. Can we remove this line in the meanwhile? It reloads and then diffs+batch-updates which is pretty wasteful.

Does it crash w/out this feature? Like if you just reload the readme on the repo you outlined.

[BrianLitwin]

yes, this was the line that prevented a crash on the particular repo/README I mentioned... without this line, It was crashing on about ~10% of repos that i manually tested, so prob should resolve the underlying issue before merging. I put a comment below with more detail + a unit test, crash log.

[rnystrom]

It’s fine to solve it in another PR. We can hold before sending another TF build. I’d like to keep PRs focused on one thing for the most part. Say the fix causes a regression, reverting the fix in this case would revert the whole feature.

[rnystrom]

nit: can you make the setter private?

[rnystrom]

nit on this whole function: params on newline. ex:

UIAlertAction(
    title: NSLocalizedString("Switch Branch", comment: ""),
    style: .default
)

[BrianLitwin]

This gist here is that calling fetch(page:) twice cases a crash with certain README markdown content unless you directly called adapter.reloadData() before update(animated:)

Would have included a form of this test in the PR but it's shoddy.. had to subclass RepositoryOverviewViewController, overrode fetch(page:) and copied/pasted the code from the real class into the unit test to duplicate the crash..

There were other repos (README's) that caused crashes, but they were consistently the same ones with the same crash error: Duplicate identifier 8881235761306338196 for object StyledTextKit.StyledTextRenderer with object StyledTextKit.StyledTextRenderer

I can find more specific README's that crash if need be.

Failing Test

import XCTest
@testable import Freetime
import Foundation
import IGListKit
import StyledTextKit

class SwitchBranches: XCTestCase {
    
    class RepositoryOverviewViewController_Test: RepositoryOverviewViewController {
        let content: String
        let mockRepo: RepositoryDetails
        
        init(content: String) {
            self.content = content
            let githubclient = newGithubClient()
            let repoDetails = RepositoryDetails(owner: "githawkapp", name: "githawk", defaultBranch: "master", hasIssuesEnabled: true)
            self.mockRepo = repoDetails
            super.init(client: githubclient, repo: repoDetails)
        }
        
        required init?(coder aDecoder: NSCoder) {
            fatalError("init(coder:) has not been implemented")
        }
        
        override func fetch(page: NSString?) {
            
            print("fetch(page:) called ***")
            
            let models = MarkdownModels(
                content,
                owner: mockRepo.owner,
                repo: mockRepo.name,
                width: 320,
                viewerCanUpdate: false,
                contentSizeCategory: UIContentSizeCategory.preferred,
                isRoot: false,
                branch: "master"
            )
            
            let model = RepositoryReadmeModel(models: models)
            self.readme = model
            // feed.adapter.reloadData()  un-comment this line to fix crash
            self.update(animated: trueUnlessReduceMotionEnabled)
        }
        
        // this here just to get test to work real quick
        override func sectionController(model: Any, listAdapter: ListAdapter) -> ListSectionController {
            let readMESectionController = RepositoryReadmeSectionController()
            readMESectionController.inset = UIEdgeInsets.zero
            return readMESectionController
        }
    }
    
    func test() {
        let content = "# Source: [Wikipedia](https://en.wikipedia.org)\n" + "# Source: [Wikipedia](https://en.wikipedia.org)\n"
        
        // note: removing the '#'s removes the crash
        // works fine: "Source: [Wikipedia](https://en.wikipedia.org)\n" + "Source: [Wikipedia](https://en.wikipedia.org)\n"
        
        //fetch(page:) called at loadViewIfNeed()
        //crashes if you call it a second time
        
        let viewController = RepositoryOverviewViewController_Test(content: content)
        viewController.loadViewIfNeeded()
        viewController.fetch(page: nil)
    }
}

Crash Log

IGListKit/Source/Common/Internal/IGListArrayUtilsInternal.h:30
2018-09-30 07:24:15.901898-0400 Freetime[72542:2056665] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Duplicate identifier -8881235761306338196 for object StyledTextKit.StyledTextRenderer with object StyledTextKit.StyledTextRenderer'
*** First throw call stack:
(
	0   CoreFoundation                      0x000000010422129b __exceptionPreprocess + 331
	1   libobjc.A.dylib                     0x00000001037c5735 objc_exception_throw + 48
	2   CoreFoundation                      0x0000000104221022 +[NSException raise:format:arguments:] + 98
	3   Foundation                          0x00000001031c9c10 -[NSAssertionHandler handleFailureInFunction:file:lineNumber:description:] + 166
	4   IGListKit                           0x00000001029db5b8 objectsWithDuplicateIdentifiersRemoved + 1048
	5   IGListKit                           0x00000001029dabd8 __60-[IGListBindingSectionController updateAnimated:completion:]_block_invoke + 856
	6   IGListKit                           0x00000001029bf458 __57-[IGListAdapter performBatchAnimated:updates:completion:]_block_invoke + 136
	7   IGListKit                           0x00000001029ce0d7 -[IGListAdapterUpdater performUpdateWithCollectionView:animated:itemUpdates:completion:] + 1687
	8   IGListKit                           0x00000001029bf2d8 -[IGListAdapter performBatchAnimated:updates:completion:] + 1976
	9   IGListKit                           0x00000001029da6cc -[IGListBindingSectionController updateAnimated:completion:] + 1260
	10  IGListKit                           0x00000001029dc1ae -[IGListBindingSectionController didUpdateToObject:] + 766
	11  IGListKit                           0x00000001029b5090 -[IGListAdapter _updateObjects:dataSource:] + 3728
	12  IGListKit                           0x00000001029ae81c __51-[IGListAdapter performUpdatesAnimated:completion:]_block_invoke + 268
	13  IGListKit                           0x00000001029c8e80 __62-[IGListAdapterUpdater performBatchUpdatesWithCollectionView:]_block_invoke + 128
	14  IGListKit                           0x00000001029c9574 __62-[IGListAdapterUpdater performBatchUpdatesWithCollectionView:]_block_invoke.82 + 36
	15  IGListKit                           0x00000001029c7f6b -[IGListAdapterUpdater performBatchUpdatesWithCollectionView:] + 2347
	16  IGListKit                           0x00000001029cc7a1 __55-[IGListAdapterUpdater _queueUpdateWithCollectionView:]_block_invoke + 401
	17  libdispatch.dylib                   0x0000000106a2851d _dispatch_call_block_and_release + 12
	18  libdispatch.dylib                   0x0000000106a29587 _dispatch_client_callout + 8
	19  libdispatch.dylib                   0x0000000106a353bc _dispatch_main_queue_callback_4CF + 1290
	20  CoreFoundation                      0x00000001041847f9 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
	21  CoreFoundation                      0x000000010417ee86 __CFRunLoopRun + 2342
	22  CoreFoundation                      0x000000010417e221 CFRunLoopRunSpecific + 625
	23  XCTest                              0x0000000123b8656b -[XCTWaiter waitForExpectations:timeout:enforceOrder:] + 955
	24  XCTest                              0x0000000123b8985e +[XCTWaiter waitForExpectations:timeout:enforceOrder:] + 104
	25  XCTest                              0x0000000123ba6d77 -[XCTTestRunSession runTestsAndReturnError:] + 972
	26  XCTest                              0x0000000123b1525a -[XCTestDriver runTestsAndReturnError:] + 422
	27  XCTest                              0x0000000123b98fbd _XCTestMain + 1478
	28  libXCTestBundleInject.dylib         0x0000000102067bb8 __copy_helper_block_ + 0
	29  CoreFoundation                      0x0000000104184a3c __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
	30  CoreFoundation                      0x00000001041841f0 __CFRunLoopDoBlocks + 336
	31  CoreFoundation                      0x000000010417ea64 __CFRunLoopRun + 1284
	32  CoreFoundation                      0x000000010417e221 CFRunLoopRunSpecific + 625
	33  GraphicsServices                    0x000000010b64e1dd GSEventRunModal + 62
	34  UIKitCore                           0x000000010d953115 UIApplicationMain + 140
	35  Freetime                            0x0000000100e200f4 main + 68
	36  libdyld.dylib                       0x0000000106a99551 start + 1
	37  ???                                 0x0000000000000005 0x0 + 5
)

Example of full README Content that causes crash

"# The Algorithms - Python \n\n### All algorithms implemented in Python (for education)\n\nThese are for demonstration purposes only. There are many implementations of sorts in the Python standard library that are much better for performance reasons.\n\n## Sort Algorithms\n\n\n### Bubble\n![alt text][bubble-image]\n\nFrom [Wikipedia][bubble-wiki]: Bubble sort, sometimes referred to as sinking sort, is a simple sorting algorithm that repeatedly steps through the list to be sorted, compares each pair of adjacent items and swaps them if they are in the wrong order. The pass through the list is repeated until no swaps are needed, which indicates that the list is sorted.\n\n__Properties__\n* Worst case performance\tO(n^2)\n* Best case performance\tO(n)\n* Average case performance\tO(n^2)\n\n###### View the algorithm in [action][bubble-toptal]\n\n\n\n### Insertion\n![alt text][insertion-image]\n\nFrom [Wikipedia][insertion-wiki]: Insertion sort is a simple sorting algorithm that builds the final sorted array (or list) one item at a time. It is much less efficient on large lists than more advanced algorithms such as quicksort, heapsort, or merge sort.\n\n__Properties__\n* Worst case performance\tO(n^2)\n* Best case performance\tO(n)\n* Average case performance\tO(n^2)\n\n###### View the algorithm in [action][insertion-toptal]\n\n\n### Merge\n![alt text][merge-image]\n\nFrom [Wikipedia][merge-wiki]: In computer science, merge sort (also commonly spelled mergesort) is an efficient, general-purpose, comparison-based sorting algorithm. Most implementations produce a stable sort, which means that the implementation preserves the input order of equal elements in the sorted output. Mergesort is a divide and conquer algorithm that was invented by John von Neumann in 1945.\n\n__Properties__\n* Worst case performance\tO(n log n)\n* Best case performance\tO(n)\n* Average case performance\tO(n)\n\n\n###### View the algorithm in [action][merge-toptal]\n\n### Quick\n![alt text][quick-image]\n\nFrom [Wikipedia][quick-wiki]: Quicksort (sometimes called partition-exchange sort) is an efficient sorting algorithm, serving as a systematic method for placing the elements of an array in order.\n\n__Properties__\n* Worst case performance\tO(n^2)\n* Best case performance\tO(n log n) or O(n) with three-way partition\n* Average case performance\tO(n log n)\n\n###### View the algorithm in [action][quick-toptal]\n\n### Selection\n![alt text][selection-image]\n\nFrom [Wikipedia][selection-wiki]: The algorithm divides the input list into two parts: the sublist of items already sorted, which is built up from left to right at the front (left) of the list, and the sublist of items remaining to be sorted that occupy the rest of the list. Initially, the sorted sublist is empty and the unsorted sublist is the entire input list. The algorithm proceeds by finding the smallest (or largest, depending on sorting order) element in the unsorted sublist, exchanging (swapping) it with the leftmost unsorted element (putting it in sorted order), and moving the sublist boundaries one element to the right.\n\n__Properties__\n* Worst case performance\tO(n^2)\n* Best case performance\tO(n^2)\n* Average case performance\tO(n^2)\n\n###### View the algorithm in [action][selection-toptal]\n\n### Shell\n![alt text][shell-image]\n\nFrom [Wikipedia][shell-wiki]: Shellsort is a generalization of insertion sort that allows the exchange of items that are far apart. The idea is to arrange the list of elements so that, starting anywhere, considering every nth element gives a sorted list. Such a list is said to be h-sorted. Equivalently, it can be thought of as h interleaved lists, each individually sorted.\n\n__Properties__\n* Worst case performance O(nlog2 2n)\n* Best case performance O(n log n)\n* Average case performance depends on gap sequence\n\n###### View the algorithm in [action][shell-toptal]\n\n### Time-Complexity Graphs\n\nComparing the complexity of sorting algorithms (Bubble Sort, Insertion Sort, Selection Sort)\n\n[Complexity Graphs](https://github.com/prateekiiest/Python/blob/master/sorts/sortinggraphs.png)\n\n----------------------------------------------------------------------------------\n\n## Search Algorithms\n\n### Linear\n![alt text][linear-image]\n\nFrom [Wikipedia][linear-wiki]: linear search or sequential search is a method for finding a target value within a list. It sequentially checks each element of the list for the target value until a match is found or until all the elements have been searched.\n Linear search runs in at worst linear time and makes at most n comparisons, where n is the length of the list.\n\n__Properties__\n* Worst case performance\tO(n)\n* Best case performance\tO(1)\n* Average case performance\tO(n)\n* Worst case space complexity\tO(1) iterative\n\n### Binary\n![alt text][binary-image]\n\nFrom [Wikipedia][binary-wiki]: Binary search, also known as half-interval search or logarithmic search, is a search algorithm that finds the position of a target value within a sorted array. It compares the target value to the middle element of the array; if they are unequal, the half in which the target cannot lie is eliminated and the search continues on the remaining half until it is successful.\n\n__Properties__\n* Worst case performance\tO(log n)\n* Best case performance\tO(1)\n* Average case performance\tO(log n)\n* Worst case space complexity\tO(1) \n\n----------------------------------------------------------------------------------------------------------------------\n\n## Ciphers\n\n### Caesar\n![alt text][caesar]
\nIn cryptography, a **Caesar cipher**, also known as Caesar\'s cipher, the shift cipher, Caesar\'s code or Caesar shift, is one of the simplest and most widely known encryption techniques.
\nIt is **a type of substitution cipher** in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on.
\nThe method is named after **Julius Caesar**, who used it in his private correspondence.
\nThe encryption step performed by a Caesar cipher is often incorporated as part of more complex schemes, such as the Vigenère cipher, and still has modern application in the ROT13 system. As with all single-alphabet substitution ciphers, the Caesar cipher is easily broken and in modern practice offers essentially no communication security.\n###### Source: [Wikipedia](https://en.wikipedia.org/wiki/Caesar_cipher)\n\n### Vigenère\nThe **Vigenère cipher** is a method of encrypting alphabetic text by using a series of **interwoven Caesar ciphers** based on the letters of a keyword. It is **a form of polyalphabetic substitution**.
\nThe Vigenère cipher has been reinvented many times. The method was originally described by Giovan Battista Bellaso in his 1553 book La cifra del. Sig. Giovan Battista Bellaso; however, the scheme was later misattributed to Blaise de Vigenère in the 19th century, and is now widely known as the \"Vigenère cipher\".
\nThough the cipher is easy to understand and implement, for three centuries it resisted all attempts to break it; this earned it the description **le chiffre indéchiffrable**(French for \'the indecipherable cipher\'). \nMany people have tried to implement encryption schemes that are essentially Vigenère ciphers. Friedrich Kasiski was the first to publish a general method of deciphering a Vigenère cipher in 1863.\n###### Source: [Wikipedia](https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher)\n\n### Transposition\nIn cryptography, a **transposition cipher** is a method of encryption by which the positions held by units of plaintext (which are commonly characters or groups of characters) are shifted according to a regular system, so that the ciphertext constitutes a permutation of the plaintext. That is, the order of the units is changed (the plaintext is reordered).
\nMathematically a bijective function is used on the characters\' positions to encrypt and an inverse function to decrypt.\n###### Source: [Wikipedia](https://en.wikipedia.org/wiki/Transposition_cipher)\n\n[bubble-toptal]: https://www.toptal.com/developers/sorting-algorithms/bubble-sort\n[bubble-wiki]: https://en.wikipedia.org/wiki/Bubble_sort\n[bubble-image]: https://upload.wikimedia.org/wikipedia/commons/thumb/8/83/Bubblesort-edited-color.svg/220px-Bubblesort-edited-color.svg.png \"Bubble Sort\"\n\n[insertion-toptal]: https://www.toptal.com/developers/sorting-algorithms/insertion-sort\n[insertion-wiki]: https://en.wikipedia.org/wiki/Insertion_sort\n[insertion-image]: https://upload.wikimedia.org/wikipedia/commons/7/7e/Insertionsort-edited.png \"Insertion Sort\"\n\n[quick-toptal]: https://www.toptal.com/developers/sorting-algorithms/quick-sort\n[quick-wiki]: https://en.wikipedia.org/wiki/Quicksort\n[quick-image]: https://upload.wikimedia.org/wikipedia/commons/6/6a/Sorting_quicksort_anim.gif \"Quick Sort\"\n\n[merge-toptal]: https://www.toptal.com/developers/sorting-algorithms/merge-sort\n[merge-wiki]: https://en.wikipedia.org/wiki/Merge_sort\n[merge-image]: https://upload.wikimedia.org/wikipedia/commons/c/cc/Merge-sort-example-300px.gif \"Merge Sort\"\n\n[selection-toptal]: https://www.toptal.com/developers/sorting-algorithms/selection-sort\n[selection-wiki]: https://en.wikipedia.org/wiki/Selection_sort\n[selection-image]: https://upload.wikimedia.org/wikipedia/commons/thumb/b/b0/Selection_sort_animation.gif/250px-Selection_sort_animation.gif \"Selection Sort Sort\"\n\n[shell-toptal]: https://www.toptal.com/developers/sorting-algorithms/shell-sort\n[shell-wiki]: https://en.wikipedia.org/wiki/Shellsort\n[shell-image]: https://upload.wikimedia.org/wikipedia/commons/d/d8/Sorting_shellsort_anim.gif \"Shell Sort\"\n\n[linear-wiki]: https://en.wikipedia.org/wiki/Linear_search\n[linear-image]: http://www.tutorialspoint.com/data_structures_algorithms/images/linear_search.gif\n\n[binary-wiki]: https://en.wikipedia.org/wiki/Binary_search_algorithm\n[binary-image]: https://upload.wikimedia.org/wikipedia/commons/f/f7/Binary_search_into_array.png\n\n\n[caesar]: https://upload.wikimedia.org/wikipedia/commons/4/4a/Caesar_cipher_left_shift_of_3.svg\n "

[rnystrom]

Since the assert is unrelated to this feature, let’s solve that in another PR

_{Sent with GitHawk}

[BrianLitwin]

@rnystrom Requested changes are in 2nd commit. Thanks for the feedback!