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Like other projects, we also have some guidelines to keep to the
code. For Git in general, a few 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.
- Fixing style violations while working on a real change as a
preparatory clean-up step is good, but otherwise avoid useless code
churn for the sake of conforming to the style.
"Once it _is_ in the tree, it's not really worth the patch noise to
go and fix it up."
Cf. http://lkml.iu.edu/hypermail/linux/kernel/1001.3/01069.html
- Log messages to explain your changes are as important as the
changes themselves. Clearly written code and in-code comments
explain how the code works and what is assumed from the surrounding
context. The log messages explain what the changes wanted to
achieve and why the changes were necessary (more on this in the
accompanying SubmittingPatches document).
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
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 are some language
specific ones. Note that Documentation/ToolsForGit.txt document
has a collection of tips to help you use some external tools
to conform to these guidelines.
For shell scripts specifically (not exhaustive):
- We use tabs for indentation.
- Case arms are indented at the same depth as case and esac lines,
like this:
case "$variable" in
pattern1)
do this
;;
pattern2)
do that
;;
esac
- Redirection operators should be written with space before, but no
space after them. In other words, write 'echo test >"$file"'
instead of 'echo test> $file' or 'echo test > $file'. Note that
even though it is not required by POSIX to double-quote the
redirection target in a variable (as shown above), our code does so
because some versions of bash issue a warning without the quotes.
(incorrect)
cat hello > world < universe
echo hello >$world
(correct)
cat hello >world <universe
echo hello >"$world"
- 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 parsable and its exit code
is not reliable across platforms.
- 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 pattern replacement ${parameter/pattern/string}.
- We use Arithmetic Expansion $(( ... )).
- 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".
(incorrect)
if test -f hello; then
do this
fi
(correct)
if test -f hello
then
do this
fi
- If a command sequence joined with && or || or | spans multiple
lines, put each command on a separate line and put && and || and |
operators at the end of each line, rather than the start. This
means you don't need to use \ to join lines, since the above
operators imply the sequence isn't finished.
(incorrect)
grep blob verify_pack_result \
| awk -f print_1.awk \
| sort >actual &&
...
(correct)
grep blob verify_pack_result |
awk -f print_1.awk |
sort >actual &&
...
- 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,
and no space inside the parentheses. The opening "{" should also
be on the same line.
(incorrect)
my_function(){
...
(correct)
my_function () {
...
- As to use of grep, stick to a subset of BRE (namely, no \{m,n\},
[::], [==], or [..]) for portability.
- We do not use \{m,n\};
- We do not use -E;
- We do not use ? or + (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).
i18n: add infrastructure for translating Git with gettext Change the skeleton implementation of i18n in Git to one that can show localized strings to users for our C, Shell and Perl programs using either GNU libintl or the Solaris gettext implementation. This new internationalization support is enabled by default. If gettext isn't available, or if Git is compiled with NO_GETTEXT=YesPlease, Git falls back on its current behavior of showing interface messages in English. When using the autoconf script we'll auto-detect if the gettext libraries are installed and act appropriately. This change is somewhat large because as well as adding a C, Shell and Perl i18n interface we're adding a lot of tests for them, and for those tests to work we need a skeleton PO file to actually test translations. A minimal Icelandic translation is included for this purpose. Icelandic includes multi-byte characters which makes it easy to test various edge cases, and it's a language I happen to understand. The rest of the commit message goes into detail about various sub-parts of this commit. = Installation Gettext .mo files will be installed and looked for in the standard $(prefix)/share/locale path. GIT_TEXTDOMAINDIR can also be set to override that, but that's only intended to be used to test Git itself. = Perl Perl code that's to be localized should use the new Git::I18n module. It imports a __ function into the caller's package by default. Instead of using the high level Locale::TextDomain interface I've opted to use the low-level (equivalent to the C interface) Locale::Messages module, which Locale::TextDomain itself uses. Locale::TextDomain does a lot of redundant work we don't need, and some of it would potentially introduce bugs. It tries to set the $TEXTDOMAIN based on package of the caller, and has its own hardcoded paths where it'll search for messages. I found it easier just to completely avoid it rather than try to circumvent its behavior. In any case, this is an issue wholly internal Git::I18N. Its guts can be changed later if that's deemed necessary. See <AANLkTilYD_NyIZMyj9dHtVk-ylVBfvyxpCC7982LWnVd@mail.gmail.com> for a further elaboration on this topic. = Shell Shell code that's to be localized should use the git-sh-i18n library. It's basically just a wrapper for the system's gettext.sh. If gettext.sh isn't available we'll fall back on gettext(1) if it's available. The latter is available without the former on Solaris, which has its own non-GNU gettext implementation. We also need to emulate eval_gettext() there. If neither are present we'll use a dumb printf(1) fall-through wrapper. = About libcharset.h and langinfo.h We use libcharset to query the character set of the current locale if it's available. I.e. we'll use it instead of nl_langinfo if HAVE_LIBCHARSET_H is set. The GNU gettext manual recommends using langinfo.h's nl_langinfo(CODESET) to acquire the current character set, but on systems that have libcharset.h's locale_charset() using the latter is either saner, or the only option on those systems. GNU and Solaris have a nl_langinfo(CODESET), FreeBSD can use either, but MinGW and some others need to use libcharset.h's locale_charset() instead. =Credits This patch is based on work by Jeff Epler <jepler@unpythonic.net> who did the initial Makefile / C work, and a lot of comments from the Git mailing list, including Jonathan Nieder, Jakub Narebski, Johannes Sixt, Erik Faye-Lund, Peter Krefting, Junio C Hamano, Thomas Rast and others. [jc: squashed a small Makefile fix from Ramsay] Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk> Signed-off-by: Junio C Hamano <gitster@pobox.com>
11 years ago
- Use Git's gettext wrappers in git-sh-i18n to make the user
interface translatable. See "Marking strings for translation" in
po/README.
- We do not write our "test" command with "-a" and "-o" and use "&&"
or "||" to concatenate multiple "test" commands instead, because
the use of "-a/-o" is often error-prone. E.g.
test -n "$x" -a "$a" = "$b"
is buggy and breaks when $x is "=", but
test -n "$x" && test "$a" = "$b"
does not have such a problem.
- Even though "local" is not part of POSIX, we make heavy use of it
in our test suite. We do not use it in scripted Porcelains, and
hopefully nobody starts using "local" before they are reimplemented
in C ;-)
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.
- As a Git developer we assume you have a reasonably modern compiler
and we recommend you to enable the DEVELOPER makefile knob to
ensure your patch is clear of all compiler warnings we care about,
by e.g. "echo DEVELOPER=1 >>config.mak".
- We try to support a wide range of C compilers to compile Git with,
including old ones. You should not use features from newer C
standard, even if your compiler groks them.
There are a few exceptions to this guideline:
. since early 2012 with e1327023ea, we have been using an enum
definition whose last element is followed by a comma. This, like
an array initializer that ends with a trailing comma, can be used
to reduce the patch noise when adding a new identifier at the end.
. since mid 2017 with cbc0f81d, we have been using designated
initializers for struct (e.g. "struct t v = { .val = 'a' };").
. since mid 2017 with 512f41cf, we have been using designated
initializers for array (e.g. "int array[10] = { [5] = 2 }").
C99: remove hardcoded-out !HAVE_VARIADIC_MACROS code Remove the "else" branches of the HAVE_VARIADIC_MACROS macro, which have been unconditionally omitted since 765dc168882 (git-compat-util: always enable variadic macros, 2021-01-28). Since were always omitted, anyone trying to use a compiler without variadic macro support to compile a git since version git v2.31.0 or later would have had a compilation error. 10 months across a few releases since then should have been enough time for anyone who cared to run into that and report the issue. In addition to that, for anyone unsetting HAVE_VARIADIC_MACROS we've been emitting extremely verbose warnings since at least ee4512ed481 (trace2: create new combined trace facility, 2019-02-22). That's because there is no such thing as a "region_enter_printf" or "region_leave_printf" format, so at least under GCC and Clang everything that includes trace.h (almost every file) emits a couple of warnings about that. There's a large benefit to being able to have a hard dependency rely on variadic macros, the code surrounding usage.c is hard to maintain if we need to write two implementations of everything, and by relying on "__FILE__" and "__LINE__" along with "__VA_ARGS__" we can in the future make error(), die() etc. log where they were called from. We've also recently merged d67fc4bf0ba (Merge branch 'bc/require-c99', 2021-12-10) which further cements our hard dependency on C99. So let's delete the fallback code, and update our CodingGuidelines to note that we depend on this. The added bullet-point starts with lower-case for consistency with other bullet-points in that section. The diff in "trace.h" is relatively hard to read, since we need to retain the existing API docs, which were comments on the code used if HAVE_VARIADIC_MACROS was not defined. Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
7 months ago
. since early 2021 with 765dc168882, we have been using variadic
macros, mostly for printf-like trace and debug macros.
These used to be forbidden, but we have not heard any breakage
report, and they are assumed to be safe.
- Variables have to be declared at the beginning of the block, before
the first statement (i.e. -Wdeclaration-after-statement).
- Declaring a variable in the for loop "for (int i = 0; i < 10; i++)"
is still not allowed in this codebase. We are in the process of
allowing it by waiting to see that 44ba10d6 (revision: use C99
declaration of variable in for() loop, 2021-11-14) does not get
complaints. Let's revisit this around November 2022.
- 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
like "char *string, c;".
- Use whitespace around operators and keywords, but not inside
parentheses and not around functions. So:
while (condition)
func(bar + 1);
and not:
while( condition )
func (bar+1);
- Do not explicitly compare an integral value with constant 0 or '\0',
or a pointer value with constant NULL. For instance, to validate that
counted array <ptr, cnt> is initialized but has no elements, write:
if (!ptr || cnt)
BUG("empty array expected");
and not:
if (ptr == NULL || cnt != 0);
BUG("empty array expected");
- We avoid using braces unnecessarily. I.e.
if (bla) {
x = 1;
}
is frowned upon. But there are a few exceptions:
- When the statement extends over a few lines (e.g., a while loop
with an embedded conditional, or a comment). E.g.:
while (foo) {
if (x)
one();
else
two();
}
if (foo) {
/*
* This one requires some explanation,
* so we're better off with braces to make
* it obvious that the indentation is correct.
*/
doit();
}
- When there are multiple arms to a conditional and some of them
require braces, enclose even a single line block in braces for
consistency. E.g.:
if (foo) {
doit();
} else {
one();
two();
three();
}
- We try to avoid assignments in the condition of an "if" statement.
- 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.
- Multi-line comments include their delimiters on separate lines from
the text. E.g.
/*
* A very long
* multi-line comment.
*/
Note however that a comment that explains a translatable string to
translators uses a convention of starting with a magic token
C style: use standard style for "TRANSLATORS" comments Change all the "TRANSLATORS: [...]" comments in the C code to use the regular Git coding style, and amend the style guide so that the example there uses that style. This custom style was necessary back in 2010 when the gettext support was initially added, and was subsequently documented in commit cbcfd4e3ea ("i18n: mention "TRANSLATORS:" marker in Documentation/CodingGuidelines", 2014-04-18). GNU xgettext hasn't had the parsing limitation that necessitated this exception for almost 3 years. Since its 0.19 release on 2014-06-02 it's been able to recognize TRANSLATOR comments in the standard Git comment syntax[1]. Usually we'd like to keep compatibility with software that's that young, but in this case literally the only person who needs to be using a gettext newer than 3 years old is Jiang Xin (the only person who runs & commits "make pot" results), so I think in this case we can make an exception. This xgettext parsing feature was added after a thread on the Git mailing list[2] which continued on the bug-gettext[3] list, but we never subsequently changed our style & styleguide, do so. There are already longstanding changes in git that use the standard comment style & have their TRANSLATORS comments extracted properly without getting the literal "*"'s mixed up in the text, as would happen before xgettext 0.19. Commit 7ff2683253 ("builtin-am: implement -i/--interactive", 2015-08-04) added one such comment, which in commit df0617bfa7 ("l10n: git.pot: v2.6.0 round 1 (123 new, 41 removed)", 2015-09-05) got picked up in the po/git.pot file with the right format, showing that Jiang already runs a modern xgettext. The xgettext parser does not handle the sort of non-standard comment style that I'm amending here in sequencer.c, but that isn't standard Git comment syntax anyway. With this change to sequencer.c & "make pot" the comment in the pot file is now correct: #. TRANSLATORS: %s will be "revert", "cherry-pick" or -#. * "rebase -i". +#. "rebase -i". 1. http://git.savannah.gnu.org/cgit/gettext.git/commit/?id=10af7fe6bd 2. <2ce9ec406501d112e032c8208417f8100bed04c6.1397712142.git.worldhello.net@gmail.com> (https://public-inbox.org/git/2ce9ec406501d112e032c8208417f8100bed04c6.1397712142.git.worldhello.net@gmail.com/) 3. https://lists.gnu.org/archive/html/bug-gettext/2014-04/msg00016.html Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Acked-by: Jiang Xin <worldhello.net@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
5 years ago
"TRANSLATORS: ", e.g.
C style: use standard style for "TRANSLATORS" comments Change all the "TRANSLATORS: [...]" comments in the C code to use the regular Git coding style, and amend the style guide so that the example there uses that style. This custom style was necessary back in 2010 when the gettext support was initially added, and was subsequently documented in commit cbcfd4e3ea ("i18n: mention "TRANSLATORS:" marker in Documentation/CodingGuidelines", 2014-04-18). GNU xgettext hasn't had the parsing limitation that necessitated this exception for almost 3 years. Since its 0.19 release on 2014-06-02 it's been able to recognize TRANSLATOR comments in the standard Git comment syntax[1]. Usually we'd like to keep compatibility with software that's that young, but in this case literally the only person who needs to be using a gettext newer than 3 years old is Jiang Xin (the only person who runs & commits "make pot" results), so I think in this case we can make an exception. This xgettext parsing feature was added after a thread on the Git mailing list[2] which continued on the bug-gettext[3] list, but we never subsequently changed our style & styleguide, do so. There are already longstanding changes in git that use the standard comment style & have their TRANSLATORS comments extracted properly without getting the literal "*"'s mixed up in the text, as would happen before xgettext 0.19. Commit 7ff2683253 ("builtin-am: implement -i/--interactive", 2015-08-04) added one such comment, which in commit df0617bfa7 ("l10n: git.pot: v2.6.0 round 1 (123 new, 41 removed)", 2015-09-05) got picked up in the po/git.pot file with the right format, showing that Jiang already runs a modern xgettext. The xgettext parser does not handle the sort of non-standard comment style that I'm amending here in sequencer.c, but that isn't standard Git comment syntax anyway. With this change to sequencer.c & "make pot" the comment in the pot file is now correct: #. TRANSLATORS: %s will be "revert", "cherry-pick" or -#. * "rebase -i". +#. "rebase -i". 1. http://git.savannah.gnu.org/cgit/gettext.git/commit/?id=10af7fe6bd 2. <2ce9ec406501d112e032c8208417f8100bed04c6.1397712142.git.worldhello.net@gmail.com> (https://public-inbox.org/git/2ce9ec406501d112e032c8208417f8100bed04c6.1397712142.git.worldhello.net@gmail.com/) 3. https://lists.gnu.org/archive/html/bug-gettext/2014-04/msg00016.html Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Acked-by: Jiang Xin <worldhello.net@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
5 years ago
/*
* TRANSLATORS: here is a comment that explains the string to
* be translated, that follows immediately after it.
*/
_("Here is a translatable string explained by the above.");
- Double negation is often harder to understand than no negation
at all.
- There are two schools of thought when it comes to comparison,
especially inside a loop. Some people prefer to have the less stable
value on the left hand side and the more stable value on the right hand
side, e.g. if you have a loop that counts variable i down to the
lower bound,
while (i > lower_bound) {
do something;
i--;
}
Other people prefer to have the textual order of values match the
actual order of values in their comparison, so that they can
mentally draw a number line from left to right and place these
values in order, i.e.
while (lower_bound < i) {
do something;
i--;
}
Both are valid, and we use both. However, the more "stable" the
stable side becomes, the more we tend to prefer the former
(comparison with a constant, "i > 0", is an extreme example).
Just do not mix styles in the same part of the code and mimic
existing styles in the neighbourhood.
- There are two schools of thought when it comes to splitting a long
logical line into multiple lines. Some people push the second and
subsequent lines far enough to the right with tabs and align them:
if (the_beginning_of_a_very_long_expression_that_has_to ||
span_more_than_a_single_line_of ||
the_source_text) {
...
while other people prefer to align the second and the subsequent
lines with the column immediately inside the opening parenthesis,
with tabs and spaces, following our "tabstop is always a multiple
of 8" convention:
if (the_beginning_of_a_very_long_expression_that_has_to ||
span_more_than_a_single_line_of ||
the_source_text) {
...
Both are valid, and we use both. Again, just do not mix styles in
the same part of the code and mimic existing styles in the
neighbourhood.
- When splitting a long logical line, some people change line before
a binary operator, so that the result looks like a parse tree when
you turn your head 90-degrees counterclockwise:
if (the_beginning_of_a_very_long_expression_that_has_to
|| span_more_than_a_single_line_of_the_source_text) {
while other people prefer to leave the operator at the end of the
line:
if (the_beginning_of_a_very_long_expression_that_has_to ||
span_more_than_a_single_line_of_the_source_text) {
Both are valid, but we tend to use the latter more, unless the
expression gets fairly complex, in which case the former tends to
be easier to read. Again, just do not mix styles in the same part
of the code and mimic existing styles in the neighbourhood.
- When splitting a long logical line, with everything else being
equal, it is preferable to split after the operator at higher
level in the parse tree. That is, this is more preferable:
if (a_very_long_variable * that_is_used_in +
a_very_long_expression) {
...
than
if (a_very_long_variable *
that_is_used_in + a_very_long_expression) {
...
- 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 its functions and structures
in the header file that exposes the API to its callers. Use what is
in "strbuf.h" as a model for the appropriate tone and level of
detail.
- The first #include in C files, except in platform specific compat/
implementations, must be either "git-compat-util.h", "cache.h" or
"builtin.h". You do not have to include more than one of these.
- A C file must directly include the header files that declare the
functions and the types it uses, except for the functions and types
that are made available to it by including one of the header files
it must include by the previous rule.
- 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.
i18n: add infrastructure for translating Git with gettext Change the skeleton implementation of i18n in Git to one that can show localized strings to users for our C, Shell and Perl programs using either GNU libintl or the Solaris gettext implementation. This new internationalization support is enabled by default. If gettext isn't available, or if Git is compiled with NO_GETTEXT=YesPlease, Git falls back on its current behavior of showing interface messages in English. When using the autoconf script we'll auto-detect if the gettext libraries are installed and act appropriately. This change is somewhat large because as well as adding a C, Shell and Perl i18n interface we're adding a lot of tests for them, and for those tests to work we need a skeleton PO file to actually test translations. A minimal Icelandic translation is included for this purpose. Icelandic includes multi-byte characters which makes it easy to test various edge cases, and it's a language I happen to understand. The rest of the commit message goes into detail about various sub-parts of this commit. = Installation Gettext .mo files will be installed and looked for in the standard $(prefix)/share/locale path. GIT_TEXTDOMAINDIR can also be set to override that, but that's only intended to be used to test Git itself. = Perl Perl code that's to be localized should use the new Git::I18n module. It imports a __ function into the caller's package by default. Instead of using the high level Locale::TextDomain interface I've opted to use the low-level (equivalent to the C interface) Locale::Messages module, which Locale::TextDomain itself uses. Locale::TextDomain does a lot of redundant work we don't need, and some of it would potentially introduce bugs. It tries to set the $TEXTDOMAIN based on package of the caller, and has its own hardcoded paths where it'll search for messages. I found it easier just to completely avoid it rather than try to circumvent its behavior. In any case, this is an issue wholly internal Git::I18N. Its guts can be changed later if that's deemed necessary. See <AANLkTilYD_NyIZMyj9dHtVk-ylVBfvyxpCC7982LWnVd@mail.gmail.com> for a further elaboration on this topic. = Shell Shell code that's to be localized should use the git-sh-i18n library. It's basically just a wrapper for the system's gettext.sh. If gettext.sh isn't available we'll fall back on gettext(1) if it's available. The latter is available without the former on Solaris, which has its own non-GNU gettext implementation. We also need to emulate eval_gettext() there. If neither are present we'll use a dumb printf(1) fall-through wrapper. = About libcharset.h and langinfo.h We use libcharset to query the character set of the current locale if it's available. I.e. we'll use it instead of nl_langinfo if HAVE_LIBCHARSET_H is set. The GNU gettext manual recommends using langinfo.h's nl_langinfo(CODESET) to acquire the current character set, but on systems that have libcharset.h's locale_charset() using the latter is either saner, or the only option on those systems. GNU and Solaris have a nl_langinfo(CODESET), FreeBSD can use either, but MinGW and some others need to use libcharset.h's locale_charset() instead. =Credits This patch is based on work by Jeff Epler <jepler@unpythonic.net> who did the initial Makefile / C work, and a lot of comments from the Git mailing list, including Jonathan Nieder, Jakub Narebski, Johannes Sixt, Erik Faye-Lund, Peter Krefting, Junio C Hamano, Thomas Rast and others. [jc: squashed a small Makefile fix from Ramsay] Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk> Signed-off-by: Junio C Hamano <gitster@pobox.com>
11 years ago
- Use Git's gettext wrappers to make the user interface
translatable. See "Marking strings for translation" in po/README.
- Variables and functions local to a given source file should be marked
with "static". Variables that are visible to other source files
must be declared with "extern" in header files. However, function
declarations should not use "extern", as that is already the default.
- You can launch gdb around your program using the shorthand GIT_DEBUGGER.
Run `GIT_DEBUGGER=1 ./bin-wrappers/git foo` to simply use gdb as is, or
run `GIT_DEBUGGER="<debugger> <debugger-args>" ./bin-wrappers/git foo` to
use your own debugger and arguments. Example: `GIT_DEBUGGER="ddd --gdb"
./bin-wrappers/git log` (See `wrap-for-bin.sh`.)
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.
CodingGuidelines: add Python coding guidelines These are kept short by simply deferring to PEP-8. Most of the Python code in Git is already very close to this style (some things in contrib/ are not). Rationale for version suggestions: - Amongst the noise in [1], there isn't any disagreement about using 2.6 as a base (see also [2]), although Brandon Casey recently added support for 2.4 and 2.5 to git-p4 [3]. - Restricting ourselves to 2.6+ makes aiming for Python 3 compatibility significantly easier [4]. - Advocating Python 3 support in all scripts is currently unrealistic because: - 'p4 -G' provides output in a format that is very hard to use with Python 3 (and its documentation claims Python 3 is unsupported). - Mercurial does not support Python 3. - Bazaar does not support Python 3. - But we should try to make new scripts compatible with Python 3 because all new Python development is happening on version 3 and the Python community will eventually stop supporting Python 2 [5]. - Python 3.1 is required to support the 'surrogateescape' error handler for encoding/decodng filenames to/from Unicode strings and Python 3.0 is not longer supported. [1] http://thread.gmane.org/gmane.comp.version-control.git/210329 [2] http://article.gmane.org/gmane.comp.version-control.git/210429 [3] http://thread.gmane.org/gmane.comp.version-control.git/214579 [4] http://docs.python.org/3.3/howto/pyporting.html#try-to-support-python-2-6-and-newer-only [5] http://www.python.org/dev/peps/pep-0404/ Signed-off-by: Junio C Hamano <gitster@pobox.com>
10 years ago
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 2.7.
CodingGuidelines: add Python coding guidelines These are kept short by simply deferring to PEP-8. Most of the Python code in Git is already very close to this style (some things in contrib/ are not). Rationale for version suggestions: - Amongst the noise in [1], there isn't any disagreement about using 2.6 as a base (see also [2]), although Brandon Casey recently added support for 2.4 and 2.5 to git-p4 [3]. - Restricting ourselves to 2.6+ makes aiming for Python 3 compatibility significantly easier [4]. - Advocating Python 3 support in all scripts is currently unrealistic because: - 'p4 -G' provides output in a format that is very hard to use with Python 3 (and its documentation claims Python 3 is unsupported). - Mercurial does not support Python 3. - Bazaar does not support Python 3. - But we should try to make new scripts compatible with Python 3 because all new Python development is happening on version 3 and the Python community will eventually stop supporting Python 2 [5]. - Python 3.1 is required to support the 'surrogateescape' error handler for encoding/decodng filenames to/from Unicode strings and Python 3.0 is not longer supported. [1] http://thread.gmane.org/gmane.comp.version-control.git/210329 [2] http://article.gmane.org/gmane.comp.version-control.git/210429 [3] http://thread.gmane.org/gmane.comp.version-control.git/214579 [4] http://docs.python.org/3.3/howto/pyporting.html#try-to-support-python-2-6-and-newer-only [5] http://www.python.org/dev/peps/pep-0404/ Signed-off-by: Junio C Hamano <gitster@pobox.com>
10 years ago
- Where required libraries do not restrict us to Python 2, we try to
also be compatible with Python 3.1 and later.
Program Output
We make a distinction between a Git command's primary output and
output which is merely chatty feedback (for instance, status
messages, running transcript, or progress display), as well as error
messages. Roughly speaking, a Git command's primary output is that
which one might want to capture to a file or send down a pipe; its
chatty output should not interfere with these use-cases.
As such, primary output should be sent to the standard output stream
(stdout), and chatty output should be sent to the standard error
stream (stderr). Examples of commands which produce primary output
include `git log`, `git show`, and `git branch --list` which generate
output on the stdout stream.
Not all Git commands have primary output; this is often true of
commands whose main function is to perform an action. Some action
commands are silent, whereas others are chatty. An example of a
chatty action commands is `git clone` with its "Cloning into
'<path>'..." and "Checking connectivity..." status messages which it
sends to the stderr stream.
Error messages from Git commands should always be sent to the stderr
stream.
Error Messages
- Do not end error messages with a full stop.
- Do not capitalize the first word, only because it is the first word
in the message ("unable to open %s", not "Unable to open %s"). But
"SHA-3 not supported" is fine, because the reason the first word is
capitalized is not because it is at the beginning of the sentence,
but because the word would be spelled in capital letters even when
it appeared in the middle of the sentence.
- Say what the error is first ("cannot open %s", not "%s: cannot open")
Externally Visible Names
- For configuration variable names, follow the existing convention:
. The section name indicates the affected subsystem.
. The subsection name, if any, indicates which of an unbounded set
of things to set the value for.
. 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. `-`),
and are broken using bumpyCaps in documentation as a hint to the
reader.
When choosing the variable namespace, do not use variable name for
specifying possibly unbounded set of things, most notably anything
an end user can freely come up with (e.g. branch names). Instead,
use subsection names or variable values, like the existing variable
branch.<name>.description does.
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).
The documentation liberally mixes US and UK English (en_US/UK)
norms for spelling and grammar, which is somewhat unfortunate.
In an ideal world, it would have been better if it consistently
used only one and not the other, and we would have picked en_US
(if you wish to correct the English of some of the existing
documentation, please see the documentation-related advice in the
Documentation/SubmittingPatches file).
CodingGuidelines: recommend gender-neutral description Technical writing seeks to convey information with minimal friction. One way that a reader can experience friction is if they encounter a description of "a user" that is later simplified using a gendered pronoun. If the reader does not consider that pronoun to apply to them, then they can experience cognitive dissonance that removes focus from the information. Give some basic tips to guide us avoid unnecessary uses of gendered description. Using a gendered pronoun is appropriate when referring to a specific person. There are acceptable existing uses of gendered pronouns within the Git codebase, such as: * References to real people (e.g. Linus Torvalds, "the Git maintainer"). Do not misgender real people. If there is any doubt to the gender of a person, then avoid using pronouns. * References to fictional people with clear genders (e.g. Alice and Bob). * Sample text used in test cases (e.g t3702, t6432). * The official text of the GPL license contains uses of "he or she", but using singular "they" (or modifying the text in some other way) is not within the scope of the Git project. * Literal email messages in Documentation/howto/ should not be edited for grammatical concerns such as this, unless we update the entire document to fit the standard documentation format. If such an effort is taken on, then the authorship would change and no longer refer to the exact mail message. * External projects consumed in contrib/ should not deviate solely for style reasons. Recommended edits should be contributed to those projects directly. Other cases within the Git project were cleaned up by the previous changes. Co-authored-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 year ago
In order to ensure the documentation is inclusive, avoid assuming
that an unspecified example person is male or female, and think
twice before using "he", "him", "she", or "her". Here are some
tips to avoid use of gendered pronouns:
- Prefer succinctness and matter-of-factly describing functionality
in the abstract. E.g.
--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...
This practice often eliminates the need to involve human actors in
your description, but it is a good practice regardless of the
avoidance of gendered pronouns.
- When it becomes awkward to stick to this style, prefer "you" when
addressing the hypothetical user, and possibly "we" when
CodingGuidelines: recommend gender-neutral description Technical writing seeks to convey information with minimal friction. One way that a reader can experience friction is if they encounter a description of "a user" that is later simplified using a gendered pronoun. If the reader does not consider that pronoun to apply to them, then they can experience cognitive dissonance that removes focus from the information. Give some basic tips to guide us avoid unnecessary uses of gendered description. Using a gendered pronoun is appropriate when referring to a specific person. There are acceptable existing uses of gendered pronouns within the Git codebase, such as: * References to real people (e.g. Linus Torvalds, "the Git maintainer"). Do not misgender real people. If there is any doubt to the gender of a person, then avoid using pronouns. * References to fictional people with clear genders (e.g. Alice and Bob). * Sample text used in test cases (e.g t3702, t6432). * The official text of the GPL license contains uses of "he or she", but using singular "they" (or modifying the text in some other way) is not within the scope of the Git project. * Literal email messages in Documentation/howto/ should not be edited for grammatical concerns such as this, unless we update the entire document to fit the standard documentation format. If such an effort is taken on, then the authorship would change and no longer refer to the exact mail message. * External projects consumed in contrib/ should not deviate solely for style reasons. Recommended edits should be contributed to those projects directly. Other cases within the Git project were cleaned up by the previous changes. Co-authored-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 year ago
discussing how the program might react to the user. E.g.
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
versions.
- If you still need to refer to an example person that is
third-person singular, you may resort to "singular they" to avoid
"he/she/him/her", e.g.
A contributor asks their upstream to pull from them.
Note that this sounds ungrammatical and unnatural to those who
learned that "they" is only used for third-person plural, e.g.
those who learn English as a second language in some parts of the
world.
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>]
If a placeholder has multiple words, they are separated by dashes:
<new-branch-name>
--template=<template-directory>
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 bars:
[-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.
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.
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
the former, the part that should not get substituted must be
quoted/escaped.