Jeff King <peff@xxxxxxxx> writes:
> +/*
> + * Check that the string refname matches a rule of the form
> + * "{prefix}%.*s{suffix}". So "foo/bar/baz" would match the rule
> + * "foo/%.*s/baz", and return the string "bar".
> + */
> +static const char *match_parse_rule(const char *refname, const char *rule,
> + size_t *len)
> +{
> + /*
> + * Check that rule matches refname up to the first percent
> + * in the rule. This is basically skip_prefix(), but
> + * ending at percent in the prefix, rather than end-of-string.
> + */
> + do {
> + if (!*rule)
> + BUG("rev-parse rule did not have percent");
> + if (*rule == '%')
> + break;
> + } while (*refname++ == *rule++);
So, if we have refname="refs/heads/frotz" and rule="refs/%.*s", then
we'll scan refname and rule to skip over their "refs/" prefix, and
the next iteration, where post-increment moved the pointers to point
at 'h' (at the beginning of "heads/frotz") on the refname side and
'%' on the rule side, we iterate once more, notice *rule is '%', and
break out of the loop. We have refname="heads/frotz" and rule="%.*s"
If we have refname="refsXheads/frotz" and rule="refs/%.*s", after
skipping over "refs", refname points at 'X' while rule points at '/'
and the loop needs to break. Both pointers are post-incremented,
and now we have refname="heads/frotz" and rule="%.*s".
Am I reading the loop correctly? I wanted the bogus refname not to
match the rule, but without peeking back refname[-1], I cannot tell
the two cases apart at this point.
> + /*
> + * Check that we matched all the way to the "%" placeholder,
> + * and skip past it within the rule string. If so, "refname" at
> + * this point is the beginning of a potential match.
> + */
> + if (!skip_prefix(rule, "%.*s", &rule))
> + return NULL;
And we now have rule pointing at "" (i.e. "refs/%.*s" has been fully
consumed). refname points at "heads/frotz".
> + /*
> + * And now check that our suffix (if any) matches.
> + */
> + if (!strip_suffix(refname, rule, len))
> + return NULL;
> +
> + return refname; /* len set by strip_suffix() */
> +}
And the suffix "" is stripped and we yield "heads/frotz".
