GSoC Student Guidance and Project Ideas for 2016

Please see also our SummerOfCode/2016 page, which contains additional information for GSoC for this year.

1. About Mercurial

• What is Mercurial? Mercurial is a free, distributed source control management tool. It efficiently handles projects of any size and offers an easy and intuitive interface.

• Why is it interesting? Besides the extremely good reasons just above, Mercurial is also interesting for many other reasons, including: a great extension system, excellent backwards compatibility, excellent documentation, ... Specifically for students, it's interesting because it offers a range of topics to work on from low-level speed optimizations all the way up to a web interface.

• Who uses it? Mercurial is used by individuals, organizations and companies all over the world. The same goes for contributors: in the open source community, a well-known organization using Mercurial is the Mozilla project, but companies like Facebook, Google and many others also contribute to Mercurial.

• What language is it written in? Mercurial is mostly written in Python. We rewrite some parts that are very performance-sensitive in C.

2. Contacting the Mercurial developers

The following channels are used by default for communication. Please use them to introduce yourself!

• IRC: many developers chat and discuss planned changes to Mercurial here. Keep in mind that most developers are in US timezones, so it might take quite a bit of time (hours) to get a response outside of those timezones!

• The developer mailing list: this list is mostly used to submit patches and discuss them.

3. Getting started/Candidate checklist

All candidates should do the following before completing their application:

1. Check the SummerOfCode/Ideas2016 page

2. Subscribe to this page to get email when it changes

3. Introduce yourself on IRC

4. Introduce yourself on the mailing list

5. Read the ContributingChanges pages.

6. Look at the easy bugs list and contribute a patch. Feel free to ask questions on IRC or the mailing list while getting started!

4. Things we look for in a candidate

• Demonstrates understanding of our tools, procedures, and source code by successfully submitting patches (see last step above)
• Participates in the community, especially via IRC
• Makes a commitment to work on GSoC full-time
• Gives an indication that she or he enjoys working with Mercurial enough to become a long-term contributor, after GSoC is over.

5. GSoC ideas

Here are some ideas of possible 2016 summer project ideas for Mercurial. Your own ideas are welcome. You may decide to work on these ideas or use them as a starting point for your own.

5.1. Example Project

• Project description: This is an example project. Please add a clear description with some details about the idea.

• Skills: Specific programming languages, domain-specific knowledge... For example: Python, network programming

• Difficulty level: Easy/Intermediate/Difficult

• Related reading/Links: Useful links to wiki pages, specific relevant mailing list discussions or patches, ...

• Further details: Additional detail about the idea

• Point of Contact: Who wrote this proposal and could answer question about it.

• Potential mentors: mentors likely to be involved with this project

5.2. Improved handling of merge conflicts

• Project description:

  • Improve the user-friendliness of merge conflicts. Currently, a number of merge conflicts are not handled in a clean way. Rather than present the user with a number of ways to handle a conflict, Mercurial simply aborts. One example of this is directory/file conflicts. This is the case where on one side of the merge, a file is created. On the other side of the merge, a directory with the same name is created. During a merge, an obscure error pops up. This should be handled properly, by allowing the user to choose how to handle the conflict.

• Skills: Python

• Difficulty level: Difficult (?)

• Related reading/Links: http://bz.mercurial-scm.org/show_bug.cgi?id=29

• Further details: MergePlan contains more details about the exact problem and a possible path forward. Additionally, the filemerge code is most likely to be relevant.

• Point of Contact:

• Potential mentors: ?

5.3. Modernize hgweb's graph rendering

• Project description: Current graph rendering code in hgweb is pretty clunky and not very extensible or efficient. We could update it to use hgweb's own JSON API, to be faster and smarter, to show more things and to look nicer.

• Skills: Python (server-side), JavaScript (client-side)

• Difficulty level: Intermediate/Difficult

• Related reading/Links: https://bz.mercurial-scm.org/show_bug.cgi?id=4020 https://bz.mercurial-scm.org/show_bug.cgi?id=2570 (not limited to these)

• Point of Contact:

• Potential mentors: ?

A list of possible improvements

• Think up a good (extensible, self-descriptive) format for graph data to put into JSON and implement it server-side
• Update client-side code to use JSON for initial rendering and rendering on scroll-down ("infinite scroll")
• Make client-side code to render graph in chunks (will help with performance after a number of infinite-scrolls and will solve issue4020)

• Maybe use SVG instead of <canvas>

• Add (non-public) phases to commits in graph (next to branches, tags and bookmarks)
• Display special (e.g. branch-closing) commits in a different way
• Display special edges, such as source-destination of a graft
• Add an ability to see obsoleted changesets (including obsolescence edge)
• Show faded-out edge(s) from the nodes on the top of the screen if they have children (e.g. when tip is not the topmost graph node), this is already done for nodes with parents at the screen bottom

More ideas and visual decisions could be borrowed from TortoiseHg, BitBucket and Kiln.

5.4. Moving toward Python3

• Project description:

  • Upgrading the code base toward Python until we hit the actually tricky issue

    Moving Mercurial to Python is not a simple task, but we have a large amount of work that need to be done before we can hit the actual hard problems regarding bytes and unicode. The various step we need to take are described in the Python3 page.

• Skills: Python

• Difficulty level: Medium (?)

• Related reading/Links: Python3

• Further details: See Python3.

• Point of Contact: Greg Szorc, Augie Fackler

• Potential mentors: ?

5.5. Implement templating for more commands

• Project description: Implement templates for all commands that output information.

  • hg log famously has a flexible templating language. All commands that output information should leverage this to provide fully customizable output, from bookmarks to blame.

• Skills: Python

• Difficulty level: Moderate (?)

• Related reading/Links:

• Further details:

• Point of Contact:

• Potential mentors:

6. Other ideas?

Come talk to us on IRC.

CategoryGsoc