1 Contributing to Bitcoin Core
2 ============================
4 The Bitcoin Core project operates an open contributor model where anyone is
5 welcome to contribute towards development in the form of peer review, testing
6 and patches. This document explains the practical process and guidelines for
9 Firstly in terms of structure, there is no particular concept of "Core
10 developers" in the sense of privileged people. Open source often naturally
11 revolves around meritocracy where longer term contributors gain more trust from
12 the developer community. However, some hierarchy is necessary for practical
13 purposes. As such there are repository "maintainers" who are responsible for
14 merging pull requests as well as a "lead maintainer" who is responsible for the
15 release cycle, overall merging, moderation and appointment of maintainers.
21 The codebase is maintained using the "contributor workflow" where everyone
22 without exception contributes patch proposals using "pull requests". This
23 facilitates social contribution, easy testing and peer review.
25 To contribute a patch, the workflow is as follows:
31 The project coding conventions in the [developer notes](doc/developer-notes.md)
34 In general [commits should be atomic](https://en.wikipedia.org/wiki/Atomic_commit#Atomic_commit_convention)
35 and diffs should be easy to read. For this reason do not mix any formatting
36 fixes or code moves with actual code changes.
38 Commit messages should be verbose by default consisting of a short subject line
39 (50 chars max), a blank line and detailed explanatory text as separate
40 paragraph(s); unless the title alone is self-explanatory (like "Corrected typo
41 in main.cpp") then a single title line is sufficient. Commit messages should be
42 helpful to people reading your code in the future, so explain the reasoning for
43 your decisions. Further explanation [here](http://chris.beams.io/posts/git-commit/).
45 If a particular commit references another issue, please add the reference, for
46 example `refs #1234`, or `fixes #4321`. Using the `fixes` or `closes` keywords
47 will cause the corresponding issue to be closed when the pull request is merged.
49 Please refer to the [Git manual](https://git-scm.com/doc) for more information
52 - Push changes to your fork
55 The title of the pull request should be prefixed by the component or area that
56 the pull request affects. Examples:
58 Consensus: Add new opcode for BIP-XXXX OP_CHECKAWESOMESIG
59 Net: Automatically create hidden service, listen on Tor
60 Qt: Add feed bump button
61 Trivial: Fix typo in main.cpp
63 If a pull request is specifically not to be considered for merging (yet) please
64 prefix the title with [WIP] or use [Tasks Lists](https://help.github.com/articles/basic-writing-and-formatting-syntax/#task-lists)
65 in the body of the pull request to indicate tasks are pending.
67 The body of the pull request should contain enough description about what the
68 patch does together with any justification/reasoning. You should include
69 references to any discussions (for example other tickets or mailing list
72 At this stage one should expect comments and review from other contributors. You
73 can add more commits to your pull request by committing them locally and pushing
74 to your fork until you have satisfied all feedback.
77 ---------------------------
78 If your pull request is accepted for merging, you may be asked by a maintainer
79 to squash and or [rebase](https://git-scm.com/docs/git-rebase) your commits
80 before it will be merged. The basic squashing workflow is shown below.
82 git checkout your_branch_name
84 # n is normally the number of commits in the pull
85 # set commits from 'pick' to 'squash', save and quit
86 # on the next screen, edit/refine commit messages
88 git push -f # (force push to GitHub)
90 If you have problems with squashing (or other workflows with `git`), you can
91 alternatively enable "Allow edits from maintainers" in the right GitHub
92 sidebar and ask for help in the pull request.
94 Please refrain from creating several pull requests for the same change.
95 Use the pull request that is already open (or was created earlier) to amend
96 changes. This preserves the discussion and review that happened earlier for
97 the respective change set.
99 The length of time required for peer review is unpredictable and will vary from
100 pull request to pull request.
103 Pull Request Philosophy
104 -----------------------
106 Patchsets should always be focused. For example, a pull request could add a
107 feature, fix a bug, or refactor code; but not a mixture. Please also avoid super
108 pull requests which attempt to do too much, are overly large, or overly complex
109 as this makes review difficult.
114 When adding a new feature, thought must be given to the long term technical debt
115 and maintenance that feature may require after inclusion. Before proposing a new
116 feature that will require maintenance, please consider if you are willing to
117 maintain it (including bug fixing). If features get orphaned with no maintainer
118 in the future, they may be removed by the Repository Maintainer.
123 Refactoring is a necessary part of any software project's evolution. The
124 following guidelines cover refactoring pull requests for the project.
126 There are three categories of refactoring, code only moves, code style fixes,
127 code refactoring. In general refactoring pull requests should not mix these
128 three kinds of activity in order to make refactoring pull requests easy to
129 review and uncontroversial. In all cases, refactoring PRs must not change the
130 behaviour of code within the pull request (bugs must be preserved as is).
132 Project maintainers aim for a quick turnaround on refactoring pull requests, so
133 where possible keep them short, uncomplex and easy to verify.
136 "Decision Making" Process
137 -------------------------
139 The following applies to code changes to the Bitcoin Core project (and related
140 projects such as libsecp256k1), and is not to be confused with overall Bitcoin
141 Network Protocol consensus changes.
143 Whether a pull request is merged into Bitcoin Core rests with the project merge
144 maintainers and ultimately the project lead.
146 Maintainers will take into consideration if a patch is in line with the general
147 principles of the project; meets the minimum standards for inclusion; and will
148 judge the general consensus of contributors.
150 In general, all pull requests must:
152 - have a clear use case, fix a demonstrable bug or serve the greater good of
153 the project (for example refactoring for modularisation);
154 - be well peer reviewed;
155 - have unit tests and functional tests where appropriate;
156 - follow code style guidelines;
157 - not break the existing test suite;
158 - where bugs are fixed, where possible, there should be unit tests
159 demonstrating the bug and also proving the fix. This helps prevent regression.
161 Patches that change Bitcoin consensus rules are considerably more involved than
162 normal because they affect the entire ecosystem and so must be preceded by
163 extensive mailing list discussions and have a numbered BIP. While each case will
164 be different, one should be prepared to expend more time and effort than for
165 other kinds of patches because of increased peer review and consensus building
171 Anyone may participate in peer review which is expressed by comments in the pull
172 request. Typically reviewers will review the code for obvious errors, as well as
173 test out the patch set and opine on the technical merits of the patch. Project
174 maintainers take into account the peer review when determining if there is
175 consensus to merge a pull request (remember that discussions may have been
176 spread out over github, mailing list and IRC discussions). The following
177 language is used within pull-request comments:
179 - ACK means "I have tested the code and I agree it should be merged";
180 - NACK means "I disagree this should be merged", and must be accompanied by
181 sound technical justification (or in certain cases of copyright/patent/licensing
182 issues, legal justification). NACKs without accompanying reasoning may be
184 - utACK means "I have not tested the code, but I have reviewed it and it looks
185 OK, I agree it can be merged";
186 - Concept ACK means "I agree in the general principle of this pull request";
187 - Nit refers to trivial, often non-blocking issues.
189 Reviewers should include the commit hash which they reviewed in their comments.
191 Project maintainers reserve the right to weigh the opinions of peer reviewers
192 using common sense judgement and also may weight based on meritocracy: Those
193 that have demonstrated a deeper commitment and understanding towards the project
194 (over time) or have clear domain expertise may naturally have more weight, as
195 one would expect in all walks of life.
197 Where a patch set affects consensus critical code, the bar will be set much
198 higher in terms of discussion and peer review requirements, keeping in mind that
199 mistakes could be very costly to the wider community. This includes refactoring
200 of consensus critical code.
202 Where a patch set proposes to change the Bitcoin consensus, it must have been
203 discussed extensively on the mailing list and IRC, be accompanied by a widely
204 discussed BIP and have a generally widely perceived technical consensus of being
205 a worthwhile change based on the judgement of the maintainers.
211 The project leader is the release manager for each Bitcoin Core release.
216 By contributing to this repository, you agree to license your work under the
217 MIT license unless specified otherwise in `contrib/debian/copyright` or at
218 the top of the file itself. Any work contributed where you are not the original
219 author must contain its license header with the original author(s) and source.