This makes it easier to distinguish between matches, mismatches, and the
various cases of inconclusive reports.
* guix/scripts/challenge.scm (<discrepancy>): Rename to...
(<comparison-report>): ... this. Add 'result' field.
(comparison-report): New macro.
(comparison-report-predicate, comparison-report-mismatch?)
(comparison-report-match?)
(comparison-report-inconclusive?): New procedures.
(discrepancies): Rename to...
(compare-contents): ... this. Change to return a list of
<comparison-report>. Remove calls to 'warning'.
(summarize-discrepancy): Rename to...
(summarize-report): ... this. Adjust to <comparison-report>.
(guix-challenge): Likewise.
* tests/challenge.scm ("no discrepancies")
("one discrepancy"): Adjust to new API.
("inconclusive: no substitutes")
("inconclusive: no local build"): New tests.
4d8e95097e