Re: [PATCH v2 1/3] git-submodule: New subcommand 'summary' (1) - code framework

[Junio C Hamano <gitster@pobox.com>]

Junio C Hamano <gitster@pobox.com> writes:

> "Ping Yin" <pkufranky@gmail.com> writes:
> ...
>> man grep says
>>  In  basic regular expressions the metacharacters ?, +, {, |, (, and )
>> lose their special meaning; instead use the backslashed versions \?,
>> \+, \{, \|, \(, and \).
>>
>> Doen't it mean that '\|' is BRE ?
>
> It just says unlike in ERE, these characters are not special in BRE; it
> does not at all say using backslash like \?, \+, and \| makes them so.
>
> And they are not.  \(...\), \{m\}, \{m,\} and \{m,n\} are part of BRE, but
> the two you used (\+ and \|) are not.  GNU accept these two as extensions,
> but other POSIX implementations may have troubles with them.
>
>   http://www.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap09.html
>
> Please be gentle to porters to non GNU systems.  Either stay inside BRE
> (which I think we have managed to do with our usage of grep) or explicitly
> ask for ERE with "grep -E".

I think this would help people new to our codebase.

Also 

    Message-ID: <7v4pdtgjf0.fsf@gitster.siamese.dyndns.org>
    Subject: Re: [PATCH] git-filter-branch could be confused by similar names
    Date: Fri, 04 Jan 2008 17:17:39 -0800

aka

    http://article.gmane.org gmane.comp.version-control.git/69630

---

 Documentation/CodingGuidelines |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines
index 3b042db..994eb91 100644
--- a/Documentation/CodingGuidelines
+++ b/Documentation/CodingGuidelines
@@ -53,6 +53,18 @@ For shell scripts specifically (not exhaustive):
  - 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