As for more concrete guidelines, just imitate the existing code
(this is a good guideline, no matter which project you are
-contributing to). But if you must have a list of rules,
-here they 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.
+
+ - 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.
- - We use ${parameter-word} and its [-=?+] siblings, and their
- colon'ed "unset or null" form.
+ - 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 ${parameter#word} and its [#%] siblings, and their
- doubled "longest matching" form.
+ - We use POSIX compliant parameter substitutions and avoid bashisms;
+ namely:
- - We use Arithmetic Expansion $(( ... )).
+ - 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 "Substring Expansion" ${parameter:offset:length}.
- - No shell arrays.
+ - No shell arrays.
- - No strlen ${#parameter}.
+ - No strlen ${#parameter}.
- - No regexp ${parameter/pattern/string}.
+ - 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).
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
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.
+
+ - Use Git's gettext wrappers to make the user interface
+ translatable. See "Marking strings for translation" in po/README.
+
+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.