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* maint: Add Documentation/CodingGuidelines When exec() fails include the failing command in the error message RelNotes-1.5.3.5: fix another typomaint
Junio C Hamano
17 years ago
3 changed files with 114 additions and 2 deletions
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Like other projects, we also have some guidelines to keep to the |
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code. For git in general, three rough rules are: |
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- Most importantly, we never say "It's in POSIX; we'll happily |
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ignore your needs should your system not conform to it." |
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We live in the real world. |
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- However, we often say "Let's stay away from that construct, |
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it's not even in POSIX". |
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- In spite of the above two rules, we sometimes say "Although |
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this is not in POSIX, it (is so convenient | makes the code |
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much more readable | has other good characteristics) and |
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practically all the platforms we care about support it, so |
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let's use it". |
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Again, we live in the real world, and it is sometimes a |
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judgement call, the decision based more on real world |
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constraints people face than what the paper standard says. |
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As for more concrete guidelines, just imitate the existing code |
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(this is a good guideline, no matter which project you are |
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contributing to). But if you must have a list of rules, |
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here they are. |
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For shell scripts specifically (not exhaustive): |
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- We prefer $( ... ) for command substitution; unlike ``, it |
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properly nests. It should have been the way Bourne spelled |
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it from day one, but unfortunately isn't. |
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- We use ${parameter-word} and its [-=?+] siblings, and their |
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colon'ed "unset or null" form. |
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- We use ${parameter#word} and its [#%] siblings, and their |
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doubled "longest matching" form. |
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- We use Arithmetic Expansion $(( ... )). |
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- No "Substring Expansion" ${parameter:offset:length}. |
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- No shell arrays. |
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- No strlen ${#parameter}. |
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- No regexp ${parameter/pattern/string}. |
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- We do not use Process Substitution <(list) or >(list). |
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- We prefer "test" over "[ ... ]". |
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- We do not write the noiseword "function" in front of shell |
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functions. |
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For C programs: |
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- We use tabs to indent, and interpret tabs as taking up to |
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8 spaces. |
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- We try to keep to at most 80 characters per line. |
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- When declaring pointers, the star sides with the variable |
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name, i.e. "char *string", not "char* string" or |
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"char * string". This makes it easier to understand code |
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like "char *string, c;". |
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- We avoid using braces unnecessarily. I.e. |
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if (bla) { |
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x = 1; |
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} |
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is frowned upon. A gray area is when the statement extends |
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over a few lines, and/or you have a lengthy comment atop of |
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it. Also, like in the Linux kernel, if there is a long list |
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of "else if" statements, it can make sense to add braces to |
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single line blocks. |
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- Try to make your code understandable. You may put comments |
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in, but comments invariably tend to stale out when the code |
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they were describing changes. Often splitting a function |
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into two makes the intention of the code much clearer. |
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- Double negation is often harder to understand than no negation |
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at all. |
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- Some clever tricks, like using the !! operator with arithmetic |
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constructs, can be extremely confusing to others. Avoid them, |
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unless there is a compelling reason to use them. |
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- Use the API. No, really. We have a strbuf (variable length |
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string), several arrays with the ALLOC_GROW() macro, a |
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path_list for sorted string lists, a hash map (mapping struct |
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objects) named "struct decorate", amongst other things. |
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- When you come up with an API, document it. |
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- The first #include in C files, except in platform specific |
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compat/ implementations, should be git-compat-util.h or another |
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header file that includes it, such as cache.h or builtin.h. |
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- If you are planning a new command, consider writing it in shell |
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or perl first, so that changes in semantics can be easily |
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changed and discussed. Many git commands started out like |
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that, and a few are still scripts. |
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- Avoid introducing a new dependency into git. This means you |
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usually should stay away from scripting languages not already |
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used in the git core command set (unless your command is clearly |
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separate from it, such as an importer to convert random-scm-X |
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repositories to git). |
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