mikuchu / gitlet

Gitlet Design Document

Description

implementing a version-control system that mimics
some of the basic features of the popular system Git.

Classes and Data Structures

Commit

 Combinations of log messages, other metadata 
(commit date, author, etc.), a reference to a tree, 
and references to parent commits. The repository also maintains 
a mapping from branch heads (in this course, we've used names 
like master, proj2, etc.) to references to commits, 
so that certain important commits have symbolic names.

Instance Variables

• Message - contains the message of a commit;
• Timestamp - time at whcich a commit was created. Assigned by the constructor
• Parent - the parent commit of a commit object

SomeObj

Class to store the Object, 

Instance Variables

• HashMap - to store commits
• HashMap - to store Branch
• directory - sets directory to directory
• workingdirectory = sets directory to workingdirectory

Algorithms

###SomeObj Class

####init() Usage: java gitlet.Main init Description: new Gitlet version-control system in the current directory. Runtime: Constant Failure cases: If there is already a Gitlet version-control system in the current directory Dangerous?: No

####add() Usage: java gitlet.Main add [file name] Description: Adds a copy of the file as it currently exists to the staging area Runtime: lgN Failure cases: If the file does not exist, Dangerous?: No

####commit() Usage: java gitlet.Main commit [message] Description: Saves a snapshot of tracked files in the current commit and staging area so they can be restored at a later time, creating a new commit. Runtime: N Failure cases: If no files have been staged, abort Dangerous?: No

####rm() Usage: java gitlet.Main rm [file name] Description: Unstage the file if it is currently staged for addition. Runtime: Constant Failure cases: If there is already a Gitlet version-control system in the current directory Dangerous?: No

####log() Usage: java gitlet.Main log Description: Starting at the current head commit, display information about each commit backwards along the commit tree until the initial commit, following the first parent commit links, ignoring any second parents found in merge commits Runtime: N Failure cases: None Dangerous?: No

####global_log() Usage: java gitlet.Main global-log Description: displays information about all commits ever made. Runtime: N Failure cases: None Dangerous?: No

####find() Usage: java gitlet.Main find [commit message] Description: Prints out the ids of all commits that have the given commit message, one per line Runtime: Constant Failure cases: If no such commit exists Dangerous?: No

####status() Usage: java gitlet.Main status Description: Displays what branches currently exist, and marks the current branch with a *. Runtime: Constant Failure cases: If there is already a Gitlet version-control system in the current directory Dangerous?: No

####checkout() Usage: java gitlet.Main checkout -- [file name] java gitlet.Main checkout [commit id] -- [file name] java gitlet.Main checkout [branch name] Description:
1.Takes the version of the file as it exists in the head commit, the front of the current branch, and puts it in the working directory, overwriting the version of the file that's already there if there is one. 2.Takes the version of the file as it exists in the commit with the given id, and puts it in the working directory, overwriting the version of the file that's already there if there is one. 3.Takes all files in the commit at the head of the given branch, and puts them in the working directory, overwriting the versions of the files that are already there if they exist.

Runtime: N
Failure cases:  
        1.If the file does not exist in the previous commit, abort,
        2.If no commit with the given id exists,
        3.If no branch with that name exists

Dangerous?: Yes

####branch() Usage: java gitlet.Main branch [branch name] Description: Creates a new branch with the given name, and points it at the current head node. Runtime: Constant Failure cases: If a branch with the given name already exists Dangerous?: No

####rm_branch() Usage: java gitlet.Main rm-branch [branch name] Description: Deletes the branch with the given name. Runtime: Constant Failure cases: If a branch with the given name does not exist, aborts. Dangerous?: No

####reset() Usage: java gitlet.Main reset [commit id] Description: Checks out all the files tracked by the given commit. Runtime: N Failure cases: If no commit with the given id exists Dangerous?: Yes

####merge() Usage: java gitlet.Main merge [branch name] Description: Merges files from the given branch into the current branch. Runtime: O(NlgN+D) , where N is the total number of ancestor commits for the two branches and D is the total amount of data in all the files under these commits. Failure cases: If there are staged additions or removals present,If attempting to merge a branch with itself, Dangerous?: Yes

###Commit Class ####getMessage() return the contains the message of a commit; ####getTimestamp() return time at whcich a commit was created. Assigned by the constructor ####getParrent() return the parent commit of a commit object

Persistence

*Use java.io.File and java.nio.file.Files to deal with files

• Since you are likely to keep various information in files (such as commits), you might be tempted to use apparently convenient file-system operations (such as listing a directory) to sequence through all of them. Be careful. Methods such as File.list and File.listFiles produce file names in an undefined order. If you use them to implement the log command, in particular, you can get random results.
• Windows users especially should beware that the file separator character is / on Unix (or MacOS) and '' on Windows. So if you form file names in your program by concatenating some directory names and a file name together with explicit /s or \s, you can be sure that it won't work on one system or the other. Java provides a system-dependent file separator character File.separator, as in ".gitlet" + File.separator + "something", or the multi-argument constructors to File, as in \ new File(".gitlet", "something"), which you can use in place of ".gitlet/something").