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Diffstat (limited to 'Documentation/CodingGuidelines')
| -rw-r--r-- | Documentation/CodingGuidelines | 205 |
1 files changed, 137 insertions, 68 deletions
diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines index 578587a471..1d92b2da03 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 @@ -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 |