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author | Junio C Hamano <gitster@pobox.com> | 2011-11-23 13:28:53 -0800 |
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committer | Junio C Hamano <gitster@pobox.com> | 2011-11-23 13:28:53 -0800 |
commit | 3686aa1caf907d22fe318c28efe93f0e7870ba50 (patch) | |
tree | f99a303bd14c7343be7ccc5b9df5382f1bf79246 /Documentation/CodingGuidelines | |
parent | imap-send: Remove unused 'use_namespace' variable (diff) | |
parent | documentation fix: git difftool uses diff tools, not merge tools. (diff) | |
download | tgif-3686aa1caf907d22fe318c28efe93f0e7870ba50.tar.xz |
Merge branch 'maint' into tj/imap-send-remove-unused
* maint: (18123 commits)
documentation fix: git difftool uses diff tools, not merge tools.
Git 1.7.7.4
Makefile: add missing header file dependencies
notes merge: eliminate OUTPUT macro
mailmap: xcalloc mailmap_info
name-rev --all: do not even attempt to describe non-commit object
Git 1.7.7.3
docs: Update install-doc-quick
docs: don't mention --quiet or --exit-code in git-log(1)
Git 1.7.7.2
t7511: avoid use of reserved filename on Windows.
clone: Quote user supplied path in a single quote pair
read-cache.c: fix index memory allocation
make the sample pre-commit hook script reject names with newlines, too
Reindent closing bracket using tab instead of spaces
Git 1.7.7.1
RelNotes/1.7.7.1: setgid bit patch is about fixing "git init" via Makefile setting
gitweb: fix regression when filtering out forks
Almost ready for 1.7.7.1
pack-objects: don't traverse objects unnecessarily
...
Conflicts:
imap-send.c
Diffstat (limited to 'Documentation/CodingGuidelines')
-rw-r--r-- | Documentation/CodingGuidelines | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines new file mode 100644 index 0000000000..fe1c1e5bc2 --- /dev/null +++ b/Documentation/CodingGuidelines @@ -0,0 +1,197 @@ +Like other projects, we also have some guidelines to keep to the +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." + We live in the real world. + + - However, we often say "Let's stay away from that construct, + it's not even in POSIX". + + - In spite of the above two rules, we sometimes say "Although + this is not in POSIX, it (is so convenient | makes the code + much more readable | has other good characteristics) and + practically all the platforms we care about support it, so + let's use it". + + Again, we live in the real world, and it is sometimes a + judgement call, the decision based more on real world + constraints people face than what the paper standard says. + + +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 +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). + +But if you must have a list of rules, here they are. + +For shell scripts specifically (not exhaustive): + + - We use tabs for indentation. + + - Case arms are indented at the same depth as case and esac lines. + + - 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. + + - We use POSIX compliant parameter substitutions and avoid bashisms; + namely: + + - We use ${parameter-word} and its [-=?+] siblings, and their + colon'ed "unset or null" form. + + - We use ${parameter#word} and its [#%] siblings, and their + doubled "longest matching" form. + + - No "Substring Expansion" ${parameter:offset:length}. + + - No shell arrays. + + - No strlen ${#parameter}. + + - No pattern replacement ${parameter/pattern/string}. + + - We use Arithmetic Expansion $(( ... )). + + - Inside Arithmetic Expansion, spell shell variables with $ in front + of them, as some shells do not grok $((x)) while accepting $(($x)) + just fine (e.g. dash older than 0.5.4). + + - We do not use Process Substitution <(list) or >(list). + + - We prefer "test" over "[ ... ]". + + - We do not write the noiseword "function" in front of shell + functions. + + - As to use of grep, stick to a subset of BRE (namely, no \{m,n\}, + [::], [==], nor [..]) for portability. + + - We do not use \{m,n\}; + + - We do not use -E; + + - We do not use ? nor + (which are \{0,1\} and \{1,\} + respectively in BRE) but that goes without saying as these + are ERE elements not BRE (note that \? and \+ are not even part + of BRE -- making them accessible from BRE is a GNU extension). + +For C programs: + + - We use tabs to indent, and interpret tabs as taking up to + 8 spaces. + + - We try to keep to at most 80 characters per line. + + - 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 + like "char *string, c;". + + - We avoid using braces unnecessarily. I.e. + + if (bla) { + x = 1; + } + + is frowned upon. A gray area is when the statement extends + over a few lines, and/or you have a lengthy comment atop of + it. Also, like in the Linux kernel, if there is a long list + of "else if" statements, it can make sense to add braces to + single line blocks. + + - We try to avoid assignments inside if(). + + - Try to make your code understandable. You may put comments + in, but comments invariably tend to stale out when the code + they were describing changes. Often splitting a function + into two makes the intention of the code much clearer. + + - Double negation is often harder to understand than no negation + at all. + + - Some clever tricks, like using the !! operator with arithmetic + constructs, can be extremely confusing to others. Avoid them, + unless there is a compelling reason to use them. + + - Use the API. No, really. We have a strbuf (variable length + string), several arrays with the ALLOC_GROW() macro, a + string_list for sorted string lists, a hash map (mapping struct + objects) named "struct decorate", amongst other things. + + - When you come up with an API, document it. + + - The first #include in C files, except in platform specific + compat/ implementations, should be git-compat-util.h or another + header file that includes it, such as cache.h or builtin.h. + + - 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 + that, and a few are still scripts. + + - 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 + separate from it, such as an importer to convert random-scm-X + repositories to git). + + - When we pass <string, length> pair to functions, we should try to + pass them in that order. + +Writing Documentation: + + 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 + 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>] + + Possibility of multiple occurrences is indicated by three dots: + <file>... + (One or more of <file>.) + + Optional parts are enclosed in square brackets: + [<extra>] + (Zero or one <extra>.) + + --exec-path[=<path>] + (Option with an optional argument. Note that the "=" is inside the + brackets.) + + [<patch>...] + (Zero or more of <patch>. Note that the dots are inside, not + outside the brackets.) + + Multiple alternatives are indicated with vertical bar: + [-q | --quiet] + [--utf8 | --no-utf8] + + Parentheses are used for grouping: + [(<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>)...] + (Any number of option -p, each with one <parent> argument.) + + 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)...[*]] + 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 + also provided. |