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1<chapter xmlns="http://docbook.org/ns/docbook"
2 xmlns:xlink="http://www.w3.org/1999/xlink"
3 xml:id="chap-conventions">
4
5<title>Coding conventions</title>
6
7
8<section xml:id="sec-syntax"><title>Syntax</title>
9
10<itemizedlist>
11
12 <listitem><para>Use 2 spaces of indentation per indentation level in
13 Nix expressions, 4 spaces in shell scripts.</para></listitem>
14
15 <listitem><para>Do not use tab characters, i.e. configure your
16 editor to use soft tabs. For instance, use <literal>(setq-default
17 indent-tabs-mode nil)</literal> in Emacs. Everybody has different
18 tab settings so it’s asking for trouble.</para></listitem>
19
20 <listitem><para>Use <literal>lowerCamelCase</literal> for variable
21 names, not <literal>UpperCamelCase</literal>. Note, this rule does
22 not apply to package attribute names, which instead follow the rules
23 in <xref linkend="sec-package-naming"/>.</para></listitem>
24
25 <listitem><para>Function calls with attribute set arguments are
26 written as
27
28<programlisting>
29foo {
30 arg = ...;
31}
32</programlisting>
33
34 not
35
36<programlisting>
37foo
38{
39 arg = ...;
40}
41</programlisting>
42
43 Also fine is
44
45<programlisting>
46foo { arg = ...; }
47</programlisting>
48
49 if it's a short call.</para></listitem>
50
51 <listitem><para>In attribute sets or lists that span multiple lines,
52 the attribute names or list elements should be aligned:
53
54<programlisting>
55# A long list.
56list =
57 [ elem1
58 elem2
59 elem3
60 ];
61
62# A long attribute set.
63attrs =
64 { attr1 = short_expr;
65 attr2 =
66 if true then big_expr else big_expr;
67 };
68
69# Alternatively:
70attrs = {
71 attr1 = short_expr;
72 attr2 =
73 if true then big_expr else big_expr;
74};
75</programlisting>
76
77 </para></listitem>
78
79 <listitem><para>Short lists or attribute sets can be written on one
80 line:
81
82<programlisting>
83# A short list.
84list = [ elem1 elem2 elem3 ];
85
86# A short set.
87attrs = { x = 1280; y = 1024; };
88</programlisting>
89
90 </para></listitem>
91
92 <listitem><para>Breaking in the middle of a function argument can
93 give hard-to-read code, like
94
95<programlisting>
96someFunction { x = 1280;
97 y = 1024; } otherArg
98 yetAnotherArg
99</programlisting>
100
101 (especially if the argument is very large, spanning multiple
102 lines).</para>
103
104 <para>Better:
105
106<programlisting>
107someFunction
108 { x = 1280; y = 1024; }
109 otherArg
110 yetAnotherArg
111</programlisting>
112
113 or
114
115<programlisting>
116let res = { x = 1280; y = 1024; };
117in someFunction res otherArg yetAnotherArg
118</programlisting>
119
120 </para></listitem>
121
122 <listitem><para>The bodies of functions, asserts, and withs are not
123 indented to prevent a lot of superfluous indentation levels, i.e.
124
125<programlisting>
126{ arg1, arg2 }:
127assert system == "i686-linux";
128stdenv.mkDerivation { ...
129</programlisting>
130
131 not
132
133<programlisting>
134{ arg1, arg2 }:
135 assert system == "i686-linux";
136 stdenv.mkDerivation { ...
137</programlisting>
138
139 </para></listitem>
140
141 <listitem><para>Function formal arguments are written as:
142
143<programlisting>
144{ arg1, arg2, arg3 }:
145</programlisting>
146
147 but if they don't fit on one line they're written as:
148
149<programlisting>
150{ arg1, arg2, arg3
151, arg4, ...
152, # Some comment...
153 argN
154}:
155</programlisting>
156
157 </para></listitem>
158
159 <listitem><para>Functions should list their expected arguments as
160 precisely as possible. That is, write
161
162<programlisting>
163{ stdenv, fetchurl, perl }: <replaceable>...</replaceable>
164</programlisting>
165
166 instead of
167
168<programlisting>
169args: with args; <replaceable>...</replaceable>
170</programlisting>
171
172 or
173
174<programlisting>
175{ stdenv, fetchurl, perl, ... }: <replaceable>...</replaceable>
176</programlisting>
177
178 </para>
179
180 <para>For functions that are truly generic in the number of
181 arguments (such as wrappers around <varname>mkDerivation</varname>)
182 that have some required arguments, you should write them using an
183 <literal>@</literal>-pattern:
184
185<programlisting>
186{ stdenv, doCoverageAnalysis ? false, ... } @ args:
187
188stdenv.mkDerivation (args // {
189 <replaceable>...</replaceable> if doCoverageAnalysis then "bla" else "" <replaceable>...</replaceable>
190})
191</programlisting>
192
193 instead of
194
195<programlisting>
196args:
197
198args.stdenv.mkDerivation (args // {
199 <replaceable>...</replaceable> if args ? doCoverageAnalysis && args.doCoverageAnalysis then "bla" else "" <replaceable>...</replaceable>
200})
201</programlisting>
202
203 </para></listitem>
204
205</itemizedlist>
206
207</section>
208
209
210<section xml:id="sec-package-naming"><title>Package naming</title>
211
212<para>In Nixpkgs, there are generally three different names associated with a package:
213
214<itemizedlist>
215
216 <listitem><para>The <varname>name</varname> attribute of the
217 derivation (excluding the version part). This is what most users
218 see, in particular when using
219 <command>nix-env</command>.</para></listitem>
220
221 <listitem><para>The variable name used for the instantiated package
222 in <filename>all-packages.nix</filename>, and when passing it as a
223 dependency to other functions. Typically this is called the
224 <emphasis>package attribute name</emphasis>. This is what Nix
225 expression authors see. It can also be used when installing using
226 <command>nix-env -iA</command>.</para></listitem>
227
228 <listitem><para>The filename for (the directory containing) the Nix
229 expression.</para></listitem>
230
231</itemizedlist>
232
233Most of the time, these are the same. For instance, the package
234<literal>e2fsprogs</literal> has a <varname>name</varname> attribute
235<literal>"e2fsprogs-<replaceable>version</replaceable>"</literal>, is
236bound to the variable name <varname>e2fsprogs</varname> in
237<filename>all-packages.nix</filename>, and the Nix expression is in
238<filename>pkgs/os-specific/linux/e2fsprogs/default.nix</filename>.
239</para>
240
241<para>There are a few naming guidelines:
242
243<itemizedlist>
244
245 <listitem><para>Generally, try to stick to the upstream package
246 name.</para></listitem>
247
248 <listitem><para>Don’t use uppercase letters in the
249 <literal>name</literal> attribute — e.g.,
250 <literal>"mplayer-1.0rc2"</literal> instead of
251 <literal>"MPlayer-1.0rc2"</literal>.</para></listitem>
252
253 <listitem><para>The version part of the <literal>name</literal>
254 attribute <emphasis>must</emphasis> start with a digit (following a
255 dash) — e.g., <literal>"hello-0.3.1rc2"</literal>.</para></listitem>
256
257 <listitem><para>If a package is not a release but a commit from a repository, then
258 the version part of the name <emphasis>must</emphasis> be the date of that
259 (fetched) commit. The date must be in <literal>"YYYY-MM-DD"</literal> format.
260 Also append <literal>"unstable"</literal> to the name - e.g.,
261 <literal>"pkgname-unstable-2014-09-23"</literal>.</para></listitem>
262
263 <listitem><para>Dashes in the package name should be preserved in
264 new variable names, rather than converted to underscores or camel
265 cased — e.g., <varname>http-parser</varname> instead of
266 <varname>http_parser</varname> or <varname>httpParser</varname>. The
267 hyphenated style is preferred in all three package
268 names.</para></listitem>
269
270 <listitem><para>If there are multiple versions of a package, this
271 should be reflected in the variable names in
272 <filename>all-packages.nix</filename>,
273 e.g. <varname>json-c-0-9</varname> and <varname>json-c-0-11</varname>.
274 If there is an obvious “default” version, make an attribute like
275 <literal>json-c = json-c-0-9;</literal>.
276 See also <xref linkend="sec-versioning" /></para></listitem>
277
278</itemizedlist>
279
280</para>
281
282</section>
283
284
285<section xml:id="sec-organisation"><title>File naming and organisation</title>
286
287<para>Names of files and directories should be in lowercase, with
288dashes between words — not in camel case. For instance, it should be
289<filename>all-packages.nix</filename>, not
290<filename>allPackages.nix</filename> or
291<filename>AllPackages.nix</filename>.</para>
292
293<section xml:id="sec-hierarchy"><title>Hierarchy</title>
294
295<para>Each package should be stored in its own directory somewhere in
296the <filename>pkgs/</filename> tree, i.e. in
297<filename>pkgs/<replaceable>category</replaceable>/<replaceable>subcategory</replaceable>/<replaceable>...</replaceable>/<replaceable>pkgname</replaceable></filename>.
298Below are some rules for picking the right category for a package.
299Many packages fall under several categories; what matters is the
300<emphasis>primary</emphasis> purpose of a package. For example, the
301<literal>libxml2</literal> package builds both a library and some
302tools; but it’s a library foremost, so it goes under
303<filename>pkgs/development/libraries</filename>.</para>
304
305<para>When in doubt, consider refactoring the
306<filename>pkgs/</filename> tree, e.g. creating new categories or
307splitting up an existing category.</para>
308
309<variablelist>
310 <varlistentry>
311 <term>If it’s used to support <emphasis>software development</emphasis>:</term>
312 <listitem>
313 <variablelist>
314 <varlistentry>
315 <term>If it’s a <emphasis>library</emphasis> used by other packages:</term>
316 <listitem>
317 <para><filename>development/libraries</filename> (e.g. <filename>libxml2</filename>)</para>
318 </listitem>
319 </varlistentry>
320 <varlistentry>
321 <term>If it’s a <emphasis>compiler</emphasis>:</term>
322 <listitem>
323 <para><filename>development/compilers</filename> (e.g. <filename>gcc</filename>)</para>
324 </listitem>
325 </varlistentry>
326 <varlistentry>
327 <term>If it’s an <emphasis>interpreter</emphasis>:</term>
328 <listitem>
329 <para><filename>development/interpreters</filename> (e.g. <filename>guile</filename>)</para>
330 </listitem>
331 </varlistentry>
332 <varlistentry>
333 <term>If it’s a (set of) development <emphasis>tool(s)</emphasis>:</term>
334 <listitem>
335 <variablelist>
336 <varlistentry>
337 <term>If it’s a <emphasis>parser generator</emphasis> (including lexers):</term>
338 <listitem>
339 <para><filename>development/tools/parsing</filename> (e.g. <filename>bison</filename>, <filename>flex</filename>)</para>
340 </listitem>
341 </varlistentry>
342 <varlistentry>
343 <term>If it’s a <emphasis>build manager</emphasis>:</term>
344 <listitem>
345 <para><filename>development/tools/build-managers</filename> (e.g. <filename>gnumake</filename>)</para>
346 </listitem>
347 </varlistentry>
348 <varlistentry>
349 <term>Else:</term>
350 <listitem>
351 <para><filename>development/tools/misc</filename> (e.g. <filename>binutils</filename>)</para>
352 </listitem>
353 </varlistentry>
354 </variablelist>
355 </listitem>
356 </varlistentry>
357 <varlistentry>
358 <term>Else:</term>
359 <listitem>
360 <para><filename>development/misc</filename></para>
361 </listitem>
362 </varlistentry>
363 </variablelist>
364 </listitem>
365 </varlistentry>
366 <varlistentry>
367 <term>If it’s a (set of) <emphasis>tool(s)</emphasis>:</term>
368 <listitem>
369 <para>(A tool is a relatively small program, especially one intended
370 to be used non-interactively.)</para>
371 <variablelist>
372 <varlistentry>
373 <term>If it’s for <emphasis>networking</emphasis>:</term>
374 <listitem>
375 <para><filename>tools/networking</filename> (e.g. <filename>wget</filename>)</para>
376 </listitem>
377 </varlistentry>
378 <varlistentry>
379 <term>If it’s for <emphasis>text processing</emphasis>:</term>
380 <listitem>
381 <para><filename>tools/text</filename> (e.g. <filename>diffutils</filename>)</para>
382 </listitem>
383 </varlistentry>
384 <varlistentry>
385 <term>If it’s a <emphasis>system utility</emphasis>, i.e.,
386 something related or essential to the operation of a
387 system:</term>
388 <listitem>
389 <para><filename>tools/system</filename> (e.g. <filename>cron</filename>)</para>
390 </listitem>
391 </varlistentry>
392 <varlistentry>
393 <term>If it’s an <emphasis>archiver</emphasis> (which may
394 include a compression function):</term>
395 <listitem>
396 <para><filename>tools/archivers</filename> (e.g. <filename>zip</filename>, <filename>tar</filename>)</para>
397 </listitem>
398 </varlistentry>
399 <varlistentry>
400 <term>If it’s a <emphasis>compression</emphasis> program:</term>
401 <listitem>
402 <para><filename>tools/compression</filename> (e.g. <filename>gzip</filename>, <filename>bzip2</filename>)</para>
403 </listitem>
404 </varlistentry>
405 <varlistentry>
406 <term>If it’s a <emphasis>security</emphasis>-related program:</term>
407 <listitem>
408 <para><filename>tools/security</filename> (e.g. <filename>nmap</filename>, <filename>gnupg</filename>)</para>
409 </listitem>
410 </varlistentry>
411 <varlistentry>
412 <term>Else:</term>
413 <listitem>
414 <para><filename>tools/misc</filename></para>
415 </listitem>
416 </varlistentry>
417 </variablelist>
418 </listitem>
419 </varlistentry>
420 <varlistentry>
421 <term>If it’s a <emphasis>shell</emphasis>:</term>
422 <listitem>
423 <para><filename>shells</filename> (e.g. <filename>bash</filename>)</para>
424 </listitem>
425 </varlistentry>
426 <varlistentry>
427 <term>If it’s a <emphasis>server</emphasis>:</term>
428 <listitem>
429 <variablelist>
430 <varlistentry>
431 <term>If it’s a web server:</term>
432 <listitem>
433 <para><filename>servers/http</filename> (e.g. <filename>apache-httpd</filename>)</para>
434 </listitem>
435 </varlistentry>
436 <varlistentry>
437 <term>If it’s an implementation of the X Windowing System:</term>
438 <listitem>
439 <para><filename>servers/x11</filename> (e.g. <filename>xorg</filename> — this includes the client libraries and programs)</para>
440 </listitem>
441 </varlistentry>
442 <varlistentry>
443 <term>Else:</term>
444 <listitem>
445 <para><filename>servers/misc</filename></para>
446 </listitem>
447 </varlistentry>
448 </variablelist>
449 </listitem>
450 </varlistentry>
451 <varlistentry>
452 <term>If it’s a <emphasis>desktop environment</emphasis>:</term>
453 <listitem>
454 <para><filename>desktops</filename> (e.g. <filename>kde</filename>, <filename>gnome</filename>, <filename>enlightenment</filename>)</para>
455 </listitem>
456 </varlistentry>
457 <varlistentry>
458 <term>If it’s a <emphasis>window manager</emphasis>:</term>
459 <listitem>
460 <para><filename>applications/window-managers</filename> (e.g. <filename>awesome</filename>, <filename>stumpwm</filename>)</para>
461 </listitem>
462 </varlistentry>
463 <varlistentry>
464 <term>If it’s an <emphasis>application</emphasis>:</term>
465 <listitem>
466 <para>A (typically large) program with a distinct user
467 interface, primarily used interactively.</para>
468 <variablelist>
469 <varlistentry>
470 <term>If it’s a <emphasis>version management system</emphasis>:</term>
471 <listitem>
472 <para><filename>applications/version-management</filename> (e.g. <filename>subversion</filename>)</para>
473 </listitem>
474 </varlistentry>
475 <varlistentry>
476 <term>If it’s for <emphasis>video playback / editing</emphasis>:</term>
477 <listitem>
478 <para><filename>applications/video</filename> (e.g. <filename>vlc</filename>)</para>
479 </listitem>
480 </varlistentry>
481 <varlistentry>
482 <term>If it’s for <emphasis>graphics viewing / editing</emphasis>:</term>
483 <listitem>
484 <para><filename>applications/graphics</filename> (e.g. <filename>gimp</filename>)</para>
485 </listitem>
486 </varlistentry>
487 <varlistentry>
488 <term>If it’s for <emphasis>networking</emphasis>:</term>
489 <listitem>
490 <variablelist>
491 <varlistentry>
492 <term>If it’s a <emphasis>mailreader</emphasis>:</term>
493 <listitem>
494 <para><filename>applications/networking/mailreaders</filename> (e.g. <filename>thunderbird</filename>)</para>
495 </listitem>
496 </varlistentry>
497 <varlistentry>
498 <term>If it’s a <emphasis>newsreader</emphasis>:</term>
499 <listitem>
500 <para><filename>applications/networking/newsreaders</filename> (e.g. <filename>pan</filename>)</para>
501 </listitem>
502 </varlistentry>
503 <varlistentry>
504 <term>If it’s a <emphasis>web browser</emphasis>:</term>
505 <listitem>
506 <para><filename>applications/networking/browsers</filename> (e.g. <filename>firefox</filename>)</para>
507 </listitem>
508 </varlistentry>
509 <varlistentry>
510 <term>Else:</term>
511 <listitem>
512 <para><filename>applications/networking/misc</filename></para>
513 </listitem>
514 </varlistentry>
515 </variablelist>
516 </listitem>
517 </varlistentry>
518 <varlistentry>
519 <term>Else:</term>
520 <listitem>
521 <para><filename>applications/misc</filename></para>
522 </listitem>
523 </varlistentry>
524 </variablelist>
525 </listitem>
526 </varlistentry>
527 <varlistentry>
528 <term>If it’s <emphasis>data</emphasis> (i.e., does not have a
529 straight-forward executable semantics):</term>
530 <listitem>
531 <variablelist>
532 <varlistentry>
533 <term>If it’s a <emphasis>font</emphasis>:</term>
534 <listitem>
535 <para><filename>data/fonts</filename></para>
536 </listitem>
537 </varlistentry>
538 <varlistentry>
539 <term>If it’s related to <emphasis>SGML/XML processing</emphasis>:</term>
540 <listitem>
541 <variablelist>
542 <varlistentry>
543 <term>If it’s an <emphasis>XML DTD</emphasis>:</term>
544 <listitem>
545 <para><filename>data/sgml+xml/schemas/xml-dtd</filename> (e.g. <filename>docbook</filename>)</para>
546 </listitem>
547 </varlistentry>
548 <varlistentry>
549 <term>If it’s an <emphasis>XSLT stylesheet</emphasis>:</term>
550 <listitem>
551 <para>(Okay, these are executable...)</para>
552 <para><filename>data/sgml+xml/stylesheets/xslt</filename> (e.g. <filename>docbook-xsl</filename>)</para>
553 </listitem>
554 </varlistentry>
555 </variablelist>
556 </listitem>
557 </varlistentry>
558 </variablelist>
559 </listitem>
560 </varlistentry>
561 <varlistentry>
562 <term>If it’s a <emphasis>game</emphasis>:</term>
563 <listitem>
564 <para><filename>games</filename></para>
565 </listitem>
566 </varlistentry>
567 <varlistentry>
568 <term>Else:</term>
569 <listitem>
570 <para><filename>misc</filename></para>
571 </listitem>
572 </varlistentry>
573</variablelist>
574
575</section>
576
577<section xml:id="sec-versioning"><title>Versioning</title>
578
579<para>Because every version of a package in Nixpkgs creates a
580potential maintenance burden, old versions of a package should not be
581kept unless there is a good reason to do so. For instance, Nixpkgs
582contains several versions of GCC because other packages don’t build
583with the latest version of GCC. Other examples are having both the
584latest stable and latest pre-release version of a package, or to keep
585several major releases of an application that differ significantly in
586functionality.</para>
587
588<para>If there is only one version of a package, its Nix expression
589should be named <filename>e2fsprogs/default.nix</filename>. If there
590are multiple versions, this should be reflected in the filename,
591e.g. <filename>e2fsprogs/1.41.8.nix</filename> and
592<filename>e2fsprogs/1.41.9.nix</filename>. The version in the
593filename should leave out unnecessary detail. For instance, if we
594keep the latest Firefox 2.0.x and 3.5.x versions in Nixpkgs, they
595should be named <filename>firefox/2.0.nix</filename> and
596<filename>firefox/3.5.nix</filename>, respectively (which, at a given
597point, might contain versions <literal>2.0.0.20</literal> and
598<literal>3.5.4</literal>). If a version requires many auxiliary
599files, you can use a subdirectory for each version,
600e.g. <filename>firefox/2.0/default.nix</filename> and
601<filename>firefox/3.5/default.nix</filename>.</para>
602
603<para>All versions of a package <emphasis>must</emphasis> be included
604in <filename>all-packages.nix</filename> to make sure that they
605evaluate correctly.</para>
606
607</section>
608
609</section>
610<section xml:id="sec-sources"><title>Fetching Sources</title>
611 <para>There are multiple ways to fetch a package source in nixpkgs. The
612 general guideline is that you should package sources with a high degree of
613 availability. Right now there is only one fetcher which has mirroring
614 support and that is <literal>fetchurl</literal>. Note that you should also
615 prefer protocols which have a corresponding proxy environment variable.
616 </para>
617 <para>You can find many source fetch helpers in <literal>pkgs/build-support/fetch*</literal>.
618 </para>
619 <para>In the file <literal>pkgs/top-level/all-packages.nix</literal> you can
620 find fetch helpers, these have names on the form
621 <literal>fetchFrom*</literal>. The intention of these are to provide
622 snapshot fetches but using the same api as some of the version controlled
623 fetchers from <literal>pkgs/build-support/</literal>. As an example going
624 from bad to good:
625 <itemizedlist>
626 <listitem>
627 <para>Bad: Uses <literal>git://</literal> which won't be proxied.
628<programlisting>
629src = fetchgit {
630 url = "git://github.com/NixOS/nix.git";
631 rev = "1f795f9f44607cc5bec70d1300150bfefcef2aae";
632 sha256 = "1cw5fszffl5pkpa6s6wjnkiv6lm5k618s32sp60kvmvpy7a2v9kg";
633}
634</programlisting>
635 </para>
636 </listitem>
637 <listitem>
638 <para>Better: This is ok, but an archive fetch will still be faster.
639<programlisting>
640src = fetchgit {
641 url = "https://github.com/NixOS/nix.git";
642 rev = "1f795f9f44607cc5bec70d1300150bfefcef2aae";
643 sha256 = "1cw5fszffl5pkpa6s6wjnkiv6lm5k618s32sp60kvmvpy7a2v9kg";
644}
645</programlisting>
646 </para>
647 </listitem>
648 <listitem>
649 <para>Best: Fetches a snapshot archive and you get the rev you want.
650<programlisting>
651src = fetchFromGitHub {
652 owner = "NixOS";
653 repo = "nix";
654 rev = "1f795f9f44607cc5bec70d1300150bfefcef2aae";
655 sha256 = "04yri911rj9j19qqqn6m82266fl05pz98inasni0vxr1cf1gdgv9";
656}
657</programlisting>
658 </para>
659 </listitem>
660 </itemizedlist>
661 </para>
662</section>
663
664<section xml:id="sec-patches"><title>Patches</title>
665 <para>Patches available online should be retrieved using
666 <literal>fetchpatch</literal>.</para>
667 <para>
668<programlisting>
669patches = [
670 (fetchpatch {
671 name = "fix-check-for-using-shared-freetype-lib.patch";
672 url = "http://git.ghostscript.com/?p=ghostpdl.git;a=patch;h=8f5d285";
673 sha256 = "1f0k043rng7f0rfl9hhb89qzvvksqmkrikmm38p61yfx51l325xr";
674 })
675];
676</programlisting>
677 </para>
678 <para>Otherwise, you can add a <literal>.patch</literal> file to the
679 <literal>nixpkgs</literal> repository. In the interest of keeping our
680 maintenance burden to a minimum, only patches that are unique
681 to <literal>nixpkgs</literal> should be added in this way.</para>
682<para><programlisting>
683patches = [ ./0001-changes.patch ];
684</programlisting></para>
685 <para>If you do need to do create this sort of patch file,
686 one way to do so is with git:
687 <orderedlist>
688 <listitem><para>Move to the root directory of the source code
689 you're patching.<screen>
690$ cd the/program/source</screen></para></listitem>
691 <listitem><para>If a git repository is not already present,
692 create one and stage all of the source files.<screen>
693$ git init
694$ git add .</screen></para></listitem>
695 <listitem><para>Edit some files to make whatever changes need
696 to be included in the patch.</para></listitem>
697 <listitem><para>Use git to create a diff, and pipe the output
698 to a patch file:<screen>
699$ git diff > nixpkgs/pkgs/the/package/0001-changes.patch</screen>
700 </para></listitem>
701 </orderedlist></para>
702</section>
703
704</chapter>