On Fri, Apr 10, 2020 at 09:44:56AM -0700, Junio C Hamano wrote:
> Jeff King <peff@xxxxxxxx> writes:
>
> > In general, parsing subsections accurately involves looking from both
> > the start and the end of the string, pulling out the section and key and
> > leaving the rest in the middle. But I think we can get away with this
> > left-to-right parsing because we're only interested in matching a
> > _specific_ subsection name, and a specific key. So there are no cases it
> > will handle incorrectly.
>
> In other words, if k were "branch.A.B.mergeoptions", it can only be
> the 'branch.*.mergeoptions' variable attached to branch "A.B", but
> when checking for branch=="A", the first two skip_prefix() would
> pass and the only thing that protects us from misparsing is that
> "B.mergeoptions" is not what we are looking for.
Yes, exactly.
> > The more general form would be:
> [...]
> Yes, but even with such a helper, i.e.
> [...]
> what Martin wrote, especially if it is reflowed to match the above, i.e.
> [...]
> I find it just as, if not more, easy to read.
Yeah, sorry if I was unclear; I think the left-to-right is perfectly
fine for this case.
> Where the parse_config_key() helper shines, I think, is when we do
> not have the middle level to compare against, and in that case, we
> must work only from the given key, scanning from both ends for dot.
Agreed.
Another option for known-value cases like this is to do it outside of
the callback handler, like:
char *key = xstrfmt("branch.%s.mergeoptions");
const char *value;
if (!git_config_get_string_const(key, &value))
...
free(key);
The allocation is a bit awkward, though we could hide that with a clever
helper.
Shifting from "iterate over and store config keys" to "look up config
keys on demand" is a much bigger change, though. I would only do it if
it made the rest of the code flow easier.
-Peff
