The SCC Core project operates an open contributor model where anyone is welcome to contribute towards development in the form of peer review, testing and patches. This document explains the practical process and guidelines for contributing.
Firstly in terms of structure, there is no particular concept of "Core developers" in the sense of privileged people. Open source often naturally revolves around meritocracy where longer term contributors gain more trust from the developer community. However, some hierarchy is necessary for practical purposes. As such there are repository "maintainers" who are responsible for merging pull requests as well as a "lead maintainer" who is responsible for the release cycle, overall merging, moderation and appointment of maintainers.
If you're looking for somewhere to start contributing, check out the good first issue list.
The codebase is maintained using the "contributor workflow" where everyone without exception contributes patch proposals using "pull requests". This facilitates social contribution, easy testing and peer review.
To contribute a patch, the workflow is as follows:
- Fork repository (only the first time).
- Create topic branch
- Commit patches
The project coding conventions in the developer notes must be adhered to.
In general commits should be atomic and diffs should be easy to read. For this reason do not mix any formatting fixes or code moves with actual code changes.
Commit messages should be verbose by default consisting of a short subject line (50 chars max), a blank line and detailed explanatory text as separate paragraph(s), unless the title alone is self-explanatory (like "Corrected typo in init.cpp") in which case a single title line is sufficient. Commit messages should be helpful to people reading your code in the future, so explain the reasoning for your decisions. Further explanation here.
If a particular commit references another issue, please add the reference. For
example: refs #1234 or fixes #4321. Using the fixes or closes keywords
will cause the corresponding issue to be closed when the pull request is merged.
Commit messages should never contain any @ mentions.
Please refer to the Git manual for more information about Git.
- Push changes to your fork
- Create pull request
The title of the pull request should be prefixed by the component or area that the pull request affects. Valid areas as:
- Consensus for changes to consensus critical code
- Doc for changes to the documentation
- Qt for changes to scc-qt
- Log Changes to log messages
- Mining for changes to the mining code
- Net or P2P for changes to the peer-to-peer network code
- Refactor for structural changes that do not change behavior
- RPC/REST/ZMQ for changes to the RPC, REST or ZMQ APIs
- Scripts and tools for changes to the scripts and tools
- Test for changes to the unit tests or QA tests
- Utils and libraries for changes to the utils and libraries
- Wallet for changes to the wallet code
Examples:
Consensus: Add new opcode for BIP-XXXX OP_CHECKAWESOMESIG
Net: Automatically create hidden service, listen on Tor
Qt: Add feed bump button
Log: Fix typo in log message
Note that translations should not be submitted as pull requests, please see Translation Process for more information on helping with translations.
If a pull request is not to be considered for merging (yet), please prefix the title with [WIP] or use Tasks Lists in the body of the pull request to indicate tasks are pending.
The body of the pull request should contain enough description about what the patch does together with any justification/reasoning. You should include references to any discussions (for example other tickets or mailing list discussions).
At this stage one should expect comments and review from other contributors. You can add more commits to your pull request by committing them locally and pushing to your fork until you have satisfied all feedback.
Note: Code review is a burdensome but important part of the development process, and as such, certain types of pull requests are rejected. In general, if the improvements do not warrant the review effort required, the PR has a high chance of being rejected. It is up to the PR author to convince the reviewers that the changes warrant the review effort, and if reviewers are "Concept NACK'ing" the PR, the author may need to present arguments and/or do research backing their suggested changes.
If your pull request contains fixup commits (commits that change the same line of code repeatedly) or too fine-grained commits, you may be asked to squash your commits before it will be reviewed. The basic squashing workflow is shown below.
git checkout your_branch_name
git rebase -i HEAD~n
# n is normally the number of commits in the pull request.
# Set commits (except the one in the first line) from 'pick' to 'squash', save and quit.
# On the next screen, edit/refine commit messages.
# Save and quit.
git push -f # (force push to GitHub)
Please update the resulting commit message if needed, it should read as a coherent message. In most cases this means that you should not just list the interim commits.
If you have problems with squashing (or other workflows with git), you can
alternatively enable "Allow edits from maintainers" in the right GitHub
sidebar and ask for help in the pull request.
Please refrain from creating several pull requests for the same change. Use the pull request that is already open (or was created earlier) to amend changes. This preserves the discussion and review that happened earlier for the respective change set.
The length of time required for peer review is unpredictable and will vary from pull request to pull request.
When a pull request conflicts with the target branch, you may be asked to rebase it on top of the current target branch.
The git rebase command will take care of rebuilding your commits on top of the new base.
This project aims to have a clean git history, where code changes are only made in non-merge commits. This simplifies auditability because merge commits can be assumed to not contain arbitrary code changes. Merge commits should be signed, and the resulting git tree hash must be deterministic and reproducible. The script in /contrib/verify-commits checks that.
After a rebase, reviewers are encouraged to sign off on the force push. This should be relatively straightforward with
the git range-diff tool explained in the productivity
notes. To avoid needless review churn, maintainers will
generally merge pull requests that received the most review attention first.
Patchsets should always be focused. For example, a pull request could add a feature, fix a bug, or refactor code; but not a mixture. Please also avoid super pull requests which attempt to do too much, are overly large, or overly complex as this makes review difficult.
When adding a new feature, thought must be given to the long term technical debt and maintenance that feature may require after inclusion. Before proposing a new feature that will require maintenance, please consider if you are willing to maintain it (including bug fixing). If features get orphaned with no maintainer in the future, they may be removed by the Repository Maintainer.
Refactoring is a necessary part of any software project's evolution. The following guidelines cover refactoring pull requests for the project.
There are three categories of refactoring, code only moves, code style fixes, code refactoring. In general refactoring pull requests should not mix these three kinds of activity in order to make refactoring pull requests easy to review and uncontroversial. In all cases, refactoring PRs must not change the behaviour of code within the pull request (bugs must be preserved as is).
Project maintainers aim for a quick turnaround on refactoring pull requests, so where possible keep them short, uncomplex and easy to verify.
The following applies to code changes to the SCC Core project (and related projects such as libsecp256k1), and is not to be confused with overall SCC Network Protocol consensus changes.
Whether a pull request is merged into SCC Core rests with the project merge maintainers and ultimately the project lead.
Maintainers will take into consideration if a patch is in line with the general principles of the project; meets the minimum standards for inclusion; and will judge the general consensus of contributors.
In general, all pull requests must:
- Have a clear use case, fix a demonstrable bug or serve the greater good of the project (for example refactoring for modularisation);
- Be well peer reviewed;
- Have unit tests and functional tests where appropriate;
- Follow code style guidelines (C++, functional tests);
- Not break the existing test suite;
- Where bugs are fixed, where possible, there should be unit tests demonstrating the bug and also proving the fix. This helps prevent regression.
- Change relevant comments and documentation when behaviour of code changes.
Patches that change SCC consensus rules are considerably more involved than normal because they affect the entire ecosystem and so must be preceded by extensive mailing list discussions and have a numbered BIP. While each case will be different, one should be prepared to expend more time and effort than for other kinds of patches because of increased peer review and consensus building requirements.
Anyone may participate in peer review which is expressed by comments in the pull request. Typically reviewers will review the code for obvious errors, as well as test out the patch set and opine on the technical merits of the patch. Project maintainers take into account the peer review when determining if there is consensus to merge a pull request (remember that discussions may have been spread out over GitHub, mailing list and IRC discussions).
A review can be a conceptual review, where the reviewer leaves a comment
Concept (N)ACK, meaning "I do (not) agree in the general goal of this pull request",Approach (N)ACK, meaningConcept ACK, but "I do (not) agree with the approach of this change".
After conceptual agreement on the change, code review can be provided. It is
starting with ACK BRANCH_COMMIT, where BRANCH_COMMIT is the top of the
topic branch. The review is followed by a description of how the reviewer did
the review. The following
language is used within pull-request comments:
- (t)ACK means "I have tested the code and I agree it should be merged", involving change-specific manual testing in addition to running the unit and functional tests, and in case it is not obvious how the manual testing was done, it should be described;
- NACK means "I disagree this should be merged", and must be accompanied by sound technical justification (or in certain cases of copyright/patent/licensing issues, legal justification). NACKs without accompanying reasoning may be disregarded;
- utACK means "I have not tested the code, but I have reviewed it and it looks OK, I agree it can be merged";
- Nit refers to trivial, often non-blocking issues.
Project maintainers reserve the right to weigh the opinions of peer reviewers using common sense judgement and also may weight based on meritocracy: Those that have demonstrated a deeper commitment and understanding towards the project (over time) or have clear domain expertise may naturally have more weight, as one would expect in all walks of life.
Where a patch set affects consensus critical code, the bar will be set much higher in terms of discussion and peer review requirements, keeping in mind that mistakes could be very costly to the wider community. This includes refactoring of consensus critical code.
Where a patch set proposes to change the SCC consensus, it must have been discussed extensively on the mailing list and IRC, be accompanied by a widely discussed BIP and have a generally widely perceived technical consensus of being a worthwhile change based on the judgement of the maintainers.
When someone rebases their PR, it can often be very difficult to ensure that
extra changes were not included in that force push. This changes could be anything
from merge conflicts to someone attempting to sneak something into the PR. To check
that a PR is the same before and after force push, you can use the following function.
Place this function in your ~/.bashrc. In order for this function to work, both the
before and after commits must be present locally.
function gfd() {
local fp1=$(git merge-base --fork-point develop $1)
local fp2=$(git merge-base --fork-point develop $2)
echo fp1=$fp1
echo fp2=$fp2
diff --color=always -u -I'^[^-+]' <(git diff $fp1..$1) <(git diff $fp2..$2)
}
The review process is normally fairly responsive on the SCC Core repository, however this might not always be the case. If you find that you've been waiting for a pull request to be given attention for several months, there may be a number of reasons for this, some of which you can do something about:
- It may be because of a feature freeze due to an upcoming release. During this time, only bug fixes are taken into consideration. If your pull request is a new feature, it will not be prioritized until the release is over. Wait for release.
- It may be because the changes you are suggesting do not appeal to people. Rather than nits and critique, which require effort and means they care enough to spend time on your contribution, thundering silence is a good sign of widespread (mild) dislike of a given change (because people don't assume others won't actually like the proposal). Don't take that personally, though! Instead, take another critical look at what you are suggesting and see if it: changes too much, is too broad, doesn't adhere to the developer notes, is dangerous or insecure, is messily written, etc. Identify and address any of the issues you find. Then ask e.g. on the forum or on a community discord if someone could give their opinion on the concept itself.
- It may be because your code is too complex for all but a few people. And those people may not have realized your pull request even exists. A great way to find people who are qualified and care about the code you are touching is the Git Blame feature. Simply find the person touching the code you are touching before you and see if you can find them and give them a nudge. Don't be incessant about the nudging though.
- Finally, if all else fails, ask on discord or elsewhere for someone to give your pull request a look. If you think you've been waiting an unreasonably long amount of time (month+) for no particular reason (few lines changed, etc), this is totally fine. Try to return the favor when someone else is asking for feedback on their code, and universe balances out.
Security and bug fixes can be backported from master to release
branches.
If the backport is non-trivial, it may be appropriate to open an
additional PR, to backport the change, only after the original PR
has been merged.
Otherwise, backports will be done in batches and
the maintainers will use the proper Needs backport (...) labels
when needed (the original author does not need to worry).
A backport should contain the following metadata in the commit body:
Github-Pull: #<PR number>
Rebased-From: <commit hash of the original commit>
Have a look at an example backport PR.
Also see the backport.py script.
Bitcoin Backports are an incredibly valuable part of SCC's development. Backporting allows us to easily implement new features, improvements and fixes as bitcoin implements them.
To see detailed statistics & progress see Google Sheet tracker: Bitcoin backports for SCC. You should use this sheet to find what PRs to backport and its commit.
To keep the spreadsheet up to date we need to pull merges made to Bitcoin for each version.
If you have not already, add the bitcoin repo as a remote:
git remote add bitcoin [email protected]:bitcoin/bitcoin.git
This allows you to easily cherry-pick merges and look into logs of bitcoin without switching directories.
To pull the most up-to-date merges first make sure bitcoin is up-to-date:
git fetch bitcoin
To create a text file with all the merges between two versions, use:
git log --first-parent --oneline bitcoin/<version_start>..bitcoin/<version_end> >> <filename>.txt
This will pull all the backports for <version_start> up until <version_end>.
<filename> will be the name of the file the where all the merges are written to.
The command
git log --first-parent --oneline bitcoin/0.14..bitcoin/0.15 >> backports_0.14-0.15.txt
will pull all merges made to Bitcoin version 0.14 until the start of version 15 and write to backports_0.14-0.15.txt.
In order to pull the most recent merges, that is, for a version that is not yet released, run:
git log --first-parent --oneline bitcoin/<cur_ver>..bitcoin/master >> <filename>.txt
this will pull all the merges made to Bitcoin since the release of the current version.
Opening the text file, you will notice that the merges are in ascending order with the most recent at the top. We need to reverse this order to allow us to merge them in order. Simply run:
tail -r <filename>.txt >> <filename>_rev.text
This will create a text file with all the original file's lines in descending order. We can now copy this file and paste the contents onto the Tracker.
When pasting the contents, make sure to split the values into the cells so every line is not present under commit hash.
The project leader is the release manager for each SCC Core release.
By contributing to this repository, you agree to license your work under the
MIT license unless specified otherwise in contrib/debian/copyright or at
the top of the file itself. Any work contributed where you are not the original
author must contain its license header with the original author(s) and source.