Support a rewrite syntax with form \g{n} to allow for integers to follow

[cbowman0]

Here's a proposed solution to fix #462.

[grobian]

ehhh, sweet! Thanks a lot!

Just one question, where does the \g come from? I'm not familiar with it, is it used with sed or something?

[grobian]

Oh, and since you added tests and all for completeness, could you update the configuration syntax docu too?

[grobian]

and please add Signed-off-by tag to your commit

[cbowman0]

The \g{n} syntax comes from the Backreference section of the libpcre man pages: https://pcre.org/pcre.txt

BACKREFERENCES

         \n              reference by number (can be ambiguous)
         \gn             reference by number
         \g{n}           reference by number
         \g{-n}          relative reference by number
         \k<name>        reference by name (Perl)
         \k'name'        reference by name (Perl)
         \g{name}        reference by name (Perl)
         \k{name}        reference by name (.NET)
         (?P=name)       reference by name (Python)

I'm not tied to it. It was what I found when attempting to solve our problem before realizing that carbon-c-relay doesn't use the regex library to do the substitution. The syntax can be anything that successfully allows the replacement =)

[grobian]

No this is fine, principle of least surprise I suppose. Please add the docu and Signoff so I can merge, thanks!

[cbowman0]

Did I update the carbon-c-relay.md properly? Any feedback on the wording or format?

[grobian]

can you wrap the doc at at most 80 chars please, apart from that looks perfectly fine to me

[grobian]

I actually meant only your changes, but this is fine too, thanks!