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1 | # LTTng-tools contributor's guide |
2 | ||
3 | Being an open source project, the LTTng-tools project welcomes | |
4 | contributions from anyone. This guide walks you through the process | |
5 | of contributing a patch to LTTng-tools. | |
6 | ||
7 | ||
8 | ## Getting the source code | |
9 | ||
10 | The LTTng-tools project uses [Git](https://git-scm.com/) for version | |
11 | control. The upstream Git repository URL is: | |
12 | ||
13 | git://git.lttng.org/lttng-tools.git | |
14 | ||
15 | ||
16 | ## Coding standard | |
17 | ||
18 | LTTng-tools uses the | |
19 | [Linux kernel coding style](http://www.kernel.org/doc/Documentation/CodingStyle) | |
20 | with one addition: single-line `if`/`for`/`while` statements must be | |
21 | wrapped in braces. | |
22 | ||
23 | Example: | |
24 | ||
25 | ~~~ c | |
26 | /* not good */ | |
27 | if (this == that) | |
28 | goto fail; | |
29 | ||
30 | /* good */ | |
31 | if (this == that) { | |
32 | goto fail; | |
33 | } | |
34 | ~~~ | |
35 | ||
36 | Although the LTTng-tools code base is primarily written in C, it does | |
37 | contain shell, Perl, and Python code as well. There is no official coding | |
38 | standard for these languages. However, using a style consistent with the | |
39 | rest of the code written in that language is strongly encouraged. | |
40 | ||
41 | ||
42 | ## Creating and sending a patch | |
43 | ||
44 | LTTng-tools's development flow is primarily email-based, although we | |
45 | also accept pull requests on our | |
46 | [GitHub mirror](https://github.com/lttng/lttng-tools). If you're going | |
47 | to create GitHub pull requests, make sure you still follow the | |
48 | guidelines below. | |
49 | ||
50 | Like a lot of open source projects, patches are submitted and reviewed | |
51 | on its development mailing list, | |
52 | [`lttng-dev`](http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev) | |
53 | (`lttng-dev@lists.lttng.org`). The mailing list is also used to share | |
54 | and comment on <abbr title="Request for Comments">RFC</abbr>s and answer | |
55 | user questions. | |
56 | ||
57 | Once your changes have been committed to your local branch, you may use | |
58 | Git's [`format-patch`](https://git-scm.com/docs/git-format-patch) command | |
59 | to generate a patch file. The following command line generates a | |
60 | patch from the latest commit: | |
61 | ||
62 | git format-patch -N1 -s --subject-prefix="PATCH lttng-tools" | |
63 | ||
64 | The custom `PATCH lttng-tools` subject prefix is mandatory when | |
65 | submitting patches that apply to the LTTng-tools project. | |
66 | ||
67 | The patch's subject (the commit message's first line) should: | |
68 | ||
69 | * begin with an uppercase letter | |
70 | * be written in the present tense | |
71 | * _not_ exceed 72 characters in length | |
72 | * _not_ end with a period | |
73 | * be prefixed with `Fix:` if the commit fixes a bug | |
74 | ||
75 | The commit message's body should be as detailed as possible and explain | |
76 | the reasons behind the proposed change. Any related | |
77 | [bug report(s)](https://bugs.lttng.org/projects/lttng-tools/issues) | |
78 | should be mentioned at the end of the message using the `#123` format, | |
79 | where `123` is the bug number: | |
80 | ||
81 | * Use `Refs: #123` if the patch is related to bug 123, but does not | |
82 | fix it yet. | |
83 | * Use `Fixes: #123` to signify that this patch fixes the bug. | |
84 | ||
85 | Make sure to **sign-off** your submitted patches (the `-s` argument to | |
86 | Git's `commit` and `format-patch` commands). | |
87 | ||
88 | Here's a complete example: | |
89 | ||
90 | ~~~ text | |
91 | Fix: use this instead of that in some context | |
92 | ||
93 | Ball tip jowl beef ribs shankle, leberkas venison turducken tail pork | |
94 | chop t-bone meatball tri-tip. Tongue beef ribs corned beef ball tip | |
95 | kevin ground round sausage rump meatloaf pig meatball prosciutto | |
96 | landjaeger strip steak. Pork pork belly beef. | |
97 | ||
98 | Biltong turkey porchetta filet mignon corned beef. T-bone bresaola | |
99 | shoulder meatloaf tongue kielbasa. | |
100 | ||
101 | Fixes: #321 | |
102 | Refs: #456 | |
103 | Refs: #1987 | |
104 | ||
105 | Signed-off-by: Jeanne Mance <jmeance@lttng.org> | |
106 | ~~~ | |
107 | ||
108 | Please note that patches should be **as focused as possible**. Do not, | |
109 | for instance, fix a bug and correct the indentation of an unrelated | |
110 | block of code as part of the same patch. | |
111 | ||
112 | The project contains a script, [`extras/checkpatch.pl`](extras/checkpatch.pl), | |
113 | that performs a number of checks on a patch to ensure it is ready for | |
114 | submission. Run this script on your patch and correct any reported | |
115 | errors before posting it to the mailing list: | |
116 | ||
117 | extras/checkpatch.pl --no-tree 0001-Fix...patch | |
118 | ||
119 | Once you are confident your patch meets the required guidelines, | |
120 | you may use Git's [`send-email`](https://git-scm.com/docs/git-send-email) | |
121 | command to send your patch to the mailing list: | |
122 | ||
123 | git send-email --suppress-cc=self --to lttng-dev@lists.lttng.org *.patch | |
124 | ||
125 | Make sure you are | |
126 | [subscribed](http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev) | |
127 | to the mailing list to follow and take part in discussions about your | |
128 | changes. You may join the file to an email as an attachment if you can't | |
129 | send the patch directly using <code>git send‑email</code>. | |
130 | ||
131 | ||
132 | ## Reviews | |
133 | ||
134 | Once your patch has been posted to the mailing list or as a GitHub | |
135 | pull request, other contributors may propose modifications. | |
136 | This is completely normal. This collaborative code review is an integral | |
137 | part of the open source development process in general and LTTng-tools | |
138 | makes no exception. | |
139 | ||
140 | Keep in mind that reviewing patches is a time-consuming process and, | |
141 | as such, may not be done right away. The delays may be affected by the | |
142 | current release cycle phase and the complexity of the proposed changes. | |
143 | If you think your patch might have been forgotten, please mention it on | |
144 | the [`#lttng`](irc://irc.oftc.net/lttng) IRC channel rather than | |
145 | resubmitting. | |
146 | ||
147 | ||
148 | ## Release cycle | |
149 | ||
150 | The LTTng-tools project follows a release cycle that alternates between | |
151 | development and release candidate (RC) phases. The master branch is | |
152 | feature-frozen during RC phases: only bug fixes are accepted during | |
153 | this period. However, patches adding new functionality may still be | |
154 | submitted and reviewed during the RC. The upcoming features and release | |
155 | dates are posted in a monthly digest on the mailing list. |