Re: [PATCH] git-remote-mediawiki: Fix a bug in a regexp

On Sat, Jun 8, 2013 at 10:57 PM, Jeff King [off-list ref] wrote:

On Sat, Jun 08, 2013 at 08:38:56PM +0200, Matthieu Moy wrote:

quoted

Célestin Matte [off-list ref] writes:

quoted

In Perl, '\n' is not a newline, but instead a literal backslash followed by an
"n". As the output of "rev-list --first-parent" is line-oriented, what we want
here is a newline.

This is right, but the code actually worked the way it was. I'm not
sure, but my understanding is that '\n' is the string "backslash
followed by n", but interpreted as a regexp, it is a newline.

Yes, the relevant doc (from "perldoc -f split") is:

  The pattern "/PATTERN/" may be replaced with an expression to specify
  patterns that vary at runtime.  (To do runtime compilation only once,
  use "/$variable/o".)

So it is treating "\n" as an expression and compiling the regex each
time through ...

I read this as saying only that static /PATTERN/ can also be a
composed /$PATTERN/. It does not indicate how string 'PATTERN' is
treated, nor does any other part of "perldoc -f split" make special
mention of string 'PATTERN'. In fact, the only explanation I found
regarding string 'PATTERN' is in my Camel book (3rd edition, page 796)
in a parenthesized comment:

    (... if you supply a string instead of a regular expression, it'll be
    interpreted as a regular expression anyway.)

quoted

The new code looks better than the old one, but the log message may be
improved.

Agreed. I think the best explanation is something like:

  Perl's split function takes a regex pattern argument. You can also
  feed it an expression, which is then compiled into a regex at runtime.
  It therefore works to pass your pattern via single quotes, but it is
  much less obvious to a reader that the argument is meant to be a
  regex, not a static string. Using the traditional slash-delimiters
  makes this easier to read.

Sounds good to me.