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-rw-r--r--Documentation/CodingGuidelines211
1 files changed, 140 insertions, 71 deletions
diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines
index 8d3a467..1d92b2d 100644
--- a/Documentation/CodingGuidelines
+++ b/Documentation/CodingGuidelines
@@ -188,6 +188,22 @@ For shell scripts specifically (not exhaustive):
hopefully nobody starts using "local" before they are reimplemented
in C ;-)
+ - Some versions of shell do not understand "export variable=value",
+ so we write "variable=value" and then "export variable" on two
+ separate lines.
+
+ - Some versions of dash have broken variable assignment when prefixed
+ with "local", "export", and "readonly", in that the value to be
+ assigned goes through field splitting at $IFS unless quoted.
+
+ (incorrect)
+ local variable=$value
+ local variable=$(command args)
+
+ (correct)
+ local variable="$value"
+ local variable="$(command args)"
+
- Use octal escape sequences (e.g. "\302\242"), not hexadecimal (e.g.
"\xc2\xa2") in printf format strings, since hexadecimal escape
sequences are not portable.
@@ -446,12 +462,41 @@ For C programs:
detail.
- The first #include in C files, except in platform specific compat/
- implementations and sha1dc/, must be either "git-compat-util.h" or
- one of the approved headers that includes it first for you. (The
- approved headers currently include "builtin.h",
- "t/helper/test-tool.h", "xdiff/xinclude.h", or
- "reftable/system.h"). You do not have to include more than one of
- these.
+ implementations and sha1dc/, must be <git-compat-util.h>. This
+ header file insulates other header files and source files from
+ platform differences, like which system header files must be
+ included in what order, and what C preprocessor feature macros must
+ be defined to trigger certain features we expect out of the system.
+ A collorary to this is that C files should not directly include
+ system header files themselves.
+
+ There are some exceptions, because certain group of files that
+ implement an API all have to include the same header file that
+ defines the API and it is convenient to include <git-compat-util.h>
+ there. Namely:
+
+ - the implementation of the built-in commands in the "builtin/"
+ directory that include "builtin.h" for the cmd_foo() prototype
+ definition,
+
+ - the test helper programs in the "t/helper/" directory that include
+ "t/helper/test-tool.h" for the cmd__foo() prototype definition,
+
+ - the xdiff implementation in the "xdiff/" directory that includes
+ "xdiff/xinclude.h" for the xdiff machinery internals,
+
+ - the unit test programs in "t/unit-tests/" directory that include
+ "t/unit-tests/test-lib.h" that gives them the unit-tests
+ framework, and
+
+ - the source files that implement reftable in the "reftable/"
+ directory that include "reftable/system.h" for the reftable
+ internals,
+
+ are allowed to assume that they do not have to include
+ <git-compat-util.h> themselves, as it is included as the first
+ '#include' in these header files. These headers must be the first
+ header file to be "#include"d in them, though.
- A C file must directly include the header files that declare the
functions and the types it uses, except for the functions and types
@@ -490,7 +535,7 @@ For Perl programs:
- Most of the C guidelines above apply.
- - We try to support Perl 5.8 and later ("use Perl 5.008").
+ - We try to support Perl 5.8.1 and later ("use Perl 5.008001").
- use strict and use warnings are strongly preferred.
@@ -518,7 +563,7 @@ For Perl programs:
For Python scripts:
- - We follow PEP-8 (http://www.python.org/dev/peps/pep-0008/).
+ - We follow PEP-8 (https://peps.python.org/pep-0008/).
- As a minimum, we aim to be compatible with Python 2.7.
@@ -578,7 +623,7 @@ Externally Visible Names
. The variable name describes the effect of tweaking this knob.
The section and variable names that consist of multiple words are
- formed by concatenating the words without punctuations (e.g. `-`),
+ formed by concatenating the words without punctuation marks (e.g. `-`),
and are broken using bumpyCaps in documentation as a hint to the
reader.
@@ -612,15 +657,15 @@ Writing Documentation:
- Prefer succinctness and matter-of-factly describing functionality
in the abstract. E.g.
- --short:: Emit output in the short-format.
+ `--short`:: Emit output in the short-format.
and avoid something like these overly verbose alternatives:
- --short:: Use this to emit output in the short-format.
- --short:: You can use this to get output in the short-format.
- --short:: A user who prefers shorter output could....
- --short:: Should a person and/or program want shorter output, he
- she/they/it can...
+ `--short`:: Use this to emit output in the short-format.
+ `--short`:: You can use this to get output in the short-format.
+ `--short`:: A user who prefers shorter output could....
+ `--short`:: Should a person and/or program want shorter output, he
+ she/they/it can...
This practice often eliminates the need to involve human actors in
your description, but it is a good practice regardless of the
@@ -630,12 +675,12 @@ Writing Documentation:
addressing the hypothetical user, and possibly "we" when
discussing how the program might react to the user. E.g.
- You can use this option instead of --xyz, but we might remove
+ You can use this option instead of `--xyz`, but we might remove
support for it in future versions.
while keeping in mind that you can probably be less verbose, e.g.
- Use this instead of --xyz. This option might be removed in future
+ Use this instead of `--xyz`. This option might be removed in future
versions.
- If you still need to refer to an example person that is
@@ -653,63 +698,118 @@ Writing Documentation:
The same general rule as for code applies -- imitate the existing
conventions.
- A few commented examples follow to provide reference when writing or
- modifying command usage strings and synopsis sections in the manual
- pages:
- Placeholders are spelled in lowercase and enclosed in angle brackets:
- <file>
- --sort=<key>
- --abbrev[=<n>]
+Markup:
+
+ Literal parts (e.g. use of command-line options, command names,
+ branch names, URLs, pathnames (files and directories), configuration and
+ environment variables) must be typeset as verbatim (i.e. wrapped with
+ backticks):
+ `--pretty=oneline`
+ `git rev-list`
+ `remote.pushDefault`
+ `http://git.example.com`
+ `.git/config`
+ `GIT_DIR`
+ `HEAD`
+ `umask`(2)
+
+ An environment variable must be prefixed with "$" only when referring to its
+ value and not when referring to the variable itself, in this case there is
+ nothing to add except the backticks:
+ `GIT_DIR` is specified
+ `$GIT_DIR/hooks/pre-receive`
+
+ Word phrases enclosed in `backtick characters` are rendered literally
+ and will not be further expanded. The use of `backticks` to achieve the
+ previous rule means that literal examples should not use AsciiDoc
+ escapes.
+ Correct:
+ `--pretty=oneline`
+ Incorrect:
+ `\--pretty=oneline`
+
+ Placeholders are spelled in lowercase and enclosed in
+ angle brackets surrounded by underscores:
+ _<file>_
+ _<commit>_
If a placeholder has multiple words, they are separated by dashes:
- <new-branch-name>
- --template=<template-directory>
+ _<new-branch-name>_
+ _<template-directory>_
+
+ A placeholder is not enclosed in backticks, as it is not a literal.
+
+ When needed, use a distinctive identifier for placeholders, usually
+ made of a qualification and a type:
+ _<git-dir>_
+ _<key-id>_
+
+ When literal and placeholders are mixed, each markup is applied for
+ each sub-entity. If they are stuck, a special markup, called
+ unconstrained formatting is required.
+ Unconstrained formating for placeholders is __<like-this>__
+ Unconstrained formatting for literal formatting is ++like this++
+ `--jobs` _<n>_
+ ++--sort=++__<key>__
+ __<directory>__++/.git++
+ ++remote.++__<name>__++.mirror++
+
+ caveat: ++ unconstrained format is not verbatim and may expand
+ content. Use Asciidoc escapes inside them.
+
+Synopsis Syntax
+
+ Syntax grammar is formatted neither as literal nor as placeholder.
+
+ A few commented examples follow to provide reference when writing or
+ modifying command usage strings and synopsis sections in the manual
+ pages:
Possibility of multiple occurrences is indicated by three dots:
- <file>...
+ _<file>_...
(One or more of <file>.)
Optional parts are enclosed in square brackets:
- [<file>...]
+ [_<file>_...]
(Zero or more of <file>.)
- --exec-path[=<path>]
+ ++--exec-path++[++=++__<path>__]
(Option with an optional argument. Note that the "=" is inside the
brackets.)
- [<patch>...]
+ [_<patch>_...]
(Zero or more of <patch>. Note that the dots are inside, not
outside the brackets.)
Multiple alternatives are indicated with vertical bars:
- [-q | --quiet]
- [--utf8 | --no-utf8]
+ [`-q` | `--quiet`]
+ [`--utf8` | `--no-utf8`]
Use spacing around "|" token(s), but not immediately after opening or
before closing a [] or () pair:
- Do: [-q | --quiet]
- Don't: [-q|--quiet]
+ Do: [`-q` | `--quiet`]
+ Don't: [`-q`|`--quiet`]
Don't use spacing around "|" tokens when they're used to separate the
alternate arguments of an option:
- Do: --track[=(direct|inherit)]
- Don't: --track[=(direct | inherit)]
+ Do: ++--track++[++=++(`direct`|`inherit`)]`
+ Don't: ++--track++[++=++(`direct` | `inherit`)]
Parentheses are used for grouping:
- [(<rev> | <range>)...]
+ [(_<rev>_ | _<range>_)...]
(Any number of either <rev> or <range>. Parens are needed to make
it clear that "..." pertains to both <rev> and <range>.)
- [(-p <parent>)...]
+ [(`-p` _<parent>_)...]
(Any number of option -p, each with one <parent> argument.)
- git remote set-head <name> (-a | -d | <branch>)
+ `git remote set-head` _<name>_ (`-a` | `-d` | _<branch>_)
(One and only one of "-a", "-d" or "<branch>" _must_ (no square
brackets) be provided.)
And a somewhat more contrived example:
- --diff-filter=[(A|C|D|M|R|T|U|X|B)...[*]]
+ `--diff-filter=[(A|C|D|M|R|T|U|X|B)...[*]]`
Here "=" is outside the brackets, because "--diff-filter=" is a
valid usage. "*" has its own pair of brackets, because it can
(optionally) be specified only when one or more of the letters is
@@ -720,37 +820,6 @@ Writing Documentation:
the user would type into a shell and use 'Git' (uppercase first letter)
when talking about the version control system and its properties.
- A few commented examples follow to provide reference when writing or
- modifying paragraphs or option/command explanations that contain options
- or commands:
-
- Literal examples (e.g. use of command-line options, command names,
- branch names, URLs, pathnames (files and directories), configuration and
- environment variables) must be typeset in monospace (i.e. wrapped with
- backticks):
- `--pretty=oneline`
- `git rev-list`
- `remote.pushDefault`
- `http://git.example.com`
- `.git/config`
- `GIT_DIR`
- `HEAD`
-
- An environment variable must be prefixed with "$" only when referring to its
- value and not when referring to the variable itself, in this case there is
- nothing to add except the backticks:
- `GIT_DIR` is specified
- `$GIT_DIR/hooks/pre-receive`
-
- Word phrases enclosed in `backtick characters` are rendered literally
- and will not be further expanded. The use of `backticks` to achieve the
- previous rule means that literal examples should not use AsciiDoc
- escapes.
- Correct:
- `--pretty=oneline`
- Incorrect:
- `\--pretty=oneline`
-
If some place in the documentation needs to typeset a command usage
example with inline substitutions, it is fine to use +monospaced and
inline substituted text+ instead of `monospaced literal text`, and with