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Diffstat (limited to 'Documentation/CodingGuidelines')
| -rw-r--r-- | Documentation/CodingGuidelines | 113 |
1 files changed, 107 insertions, 6 deletions
diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines index fe1c1e5bc2..559d5f9ebf 100644 --- a/Documentation/CodingGuidelines +++ b/Documentation/CodingGuidelines @@ -1,5 +1,5 @@ Like other projects, we also have some guidelines to keep to the -code. For git in general, three rough rules are: +code. For Git in general, three rough rules are: - Most importantly, we never say "It's in POSIX; we'll happily ignore your needs should your system not conform to it." @@ -18,11 +18,12 @@ code. For git in general, three rough rules are: judgement call, the decision based more on real world constraints people face than what the paper standard says. +Make your code readable and sensible, and don't try to be clever. As for more concrete guidelines, just imitate the existing code (this is a good guideline, no matter which project you are contributing to). It is always preferable to match the _local_ -convention. New code added to git suite is expected to match +convention. New code added to Git suite is expected to match the overall style of existing code. Modifications to existing code is expected to match the style the surrounding code already uses (even if it doesn't match the overall style of existing code). @@ -35,10 +36,22 @@ For shell scripts specifically (not exhaustive): - Case arms are indented at the same depth as case and esac lines. + - Redirection operators should be written with space before, but no + space after them. In other words, write 'echo test >"$file"' + instead of 'echo test> $file' or 'echo test > $file'. Note that + even though it is not required by POSIX to double-quote the + redirection target in a variable (as shown above), our code does so + because some versions of bash issue a warning without the quotes. + - We prefer $( ... ) for command substitution; unlike ``, it properly nests. It should have been the way Bourne spelled it from day one, but unfortunately isn't. + - If you want to find out if a command is available on the user's + $PATH, you should use 'type <command>', instead of 'which <command>'. + The output of 'which' is not machine parseable and its exit code + is not reliable across platforms. + - We use POSIX compliant parameter substitutions and avoid bashisms; namely: @@ -64,11 +77,19 @@ For shell scripts specifically (not exhaustive): - We do not use Process Substitution <(list) or >(list). + - Do not write control structures on a single line with semicolon. + "then" should be on the next line for if statements, and "do" + should be on the next line for "while" and "for". + - We prefer "test" over "[ ... ]". - We do not write the noiseword "function" in front of shell functions. + - We prefer a space between the function name and the parentheses. The + opening "{" should also be on the same line. + E.g.: my_function () { + - As to use of grep, stick to a subset of BRE (namely, no \{m,n\}, [::], [==], nor [..]) for portability. @@ -81,6 +102,10 @@ For shell scripts specifically (not exhaustive): are ERE elements not BRE (note that \? and \+ are not even part of BRE -- making them accessible from BRE is a GNU extension). + - Use Git's gettext wrappers in git-sh-i18n to make the user + interface translatable. See "Marking strings for translation" in + po/README. + For C programs: - We use tabs to indent, and interpret tabs as taking up to @@ -88,6 +113,14 @@ For C programs: - We try to keep to at most 80 characters per line. + - We try to support a wide range of C compilers to compile Git with, + including old ones. That means that you should not use C99 + initializers, even if a lot of compilers grok it. + + - Variables have to be declared at the beginning of the block. + + - NULL pointers shall be written as NULL, not as 0. + - When declaring pointers, the star sides with the variable name, i.e. "char *string", not "char* string" or "char * string". This makes it easier to understand code @@ -132,20 +165,83 @@ For C programs: - If you are planning a new command, consider writing it in shell or perl first, so that changes in semantics can be easily - changed and discussed. Many git commands started out like + changed and discussed. Many Git commands started out like that, and a few are still scripts. - - Avoid introducing a new dependency into git. This means you + - Avoid introducing a new dependency into Git. This means you usually should stay away from scripting languages not already - used in the git core command set (unless your command is clearly + used in the Git core command set (unless your command is clearly separate from it, such as an importer to convert random-scm-X - repositories to git). + repositories to Git). - When we pass <string, length> pair to functions, we should try to pass them in that order. + - Use Git's gettext wrappers to make the user interface + translatable. See "Marking strings for translation" in po/README. + +For Perl programs: + + - Most of the C guidelines above apply. + + - We try to support Perl 5.8 and later ("use Perl 5.008"). + + - use strict and use warnings are strongly preferred. + + - Don't overuse statement modifiers unless using them makes the + result easier to follow. + + ... do something ... + do_this() unless (condition); + ... do something else ... + + is more readable than: + + ... do something ... + unless (condition) { + do_this(); + } + ... do something else ... + + *only* when the condition is so rare that do_this() will be almost + always called. + + - We try to avoid assignments inside "if ()" conditions. + + - Learn and use Git.pm if you need that functionality. + + - For Emacs, it's useful to put the following in + GIT_CHECKOUT/.dir-locals.el, assuming you use cperl-mode: + + ;; note the first part is useful for C editing, too + ((nil . ((indent-tabs-mode . t) + (tab-width . 8) + (fill-column . 80))) + (cperl-mode . ((cperl-indent-level . 8) + (cperl-extra-newline-before-brace . nil) + (cperl-merge-trailing-else . t)))) + +For Python scripts: + + - We follow PEP-8 (http://www.python.org/dev/peps/pep-0008/). + + - As a minimum, we aim to be compatible with Python 2.6 and 2.7. + + - Where required libraries do not restrict us to Python 2, we try to + also be compatible with Python 3.1 and later. + + - When you must differentiate between Unicode literals and byte string + literals, it is OK to use the 'b' prefix. Even though the Python + documentation for version 2.6 does not mention this prefix, it has + been supported since version 2.6.0. + Writing Documentation: + Most (if not all) of the documentation pages are written in the + AsciiDoc format in *.txt files (e.g. Documentation/git.txt), and + processed into HTML and manpages (e.g. git.html and git.1 in the + same directory). + Every user-visible change should be reflected in the documentation. The same general rule as for code applies -- imitate the existing conventions. A few commented examples follow to provide reference @@ -195,3 +291,8 @@ Writing Documentation: valid usage. "*" has its own pair of brackets, because it can (optionally) be specified only when one or more of the letters is also provided. + + A note on notation: + Use 'git' (all lowercase) when talking about commands i.e. something + the user would type into a shell and use 'Git' (uppercase first letter) + when talking about the version control system and its properties. |